I will stick with you and help you out as much as I can, and I will save "most" of the lecturing for the person who put this mess together and then sold it to you for such a price. I find that to be really rude and outrageous. Did this person give you a reason why they were getting rid of it? My first guess would be that the fish are maturing and now it is becoming real work to keep them alive.
My first suggestion to you is going to be to stop all medications and salt for the time being. Do a series of 20% water changes every day for the next 5 - 6 days, and let things settle a bit. Add carbon back to the filter to help remove any medication that is left.
I can very clearly see your problem, so I will begin by breaking things down as much as possible for you. Please feel free to ask all questions you have or come up with as we progress. I will apologize in advance if some of my comments and/or suggestions are not what you are wanting or hoping to hear, but I am well known for being honest with everyone. At times I can be a bit blunt in my replies, please know that I am not intending to offend you or anyone else, that is just my personality. I also apologize now for the length of my posts, as I can already see these may get a bit long. I do my best to be as thorough as possible, for the sake of the animals, your pocketbook, and your sanity. Some people don't like that, but sometimes it is very necessary.
Ok, lets get started...
First thing first, your tank appears to be cycling, which should be expected with the move you mentioned and the full replacement of the water. In the future, that is not a healthy/good thing to do. Dirty water or not, you should always try to keep as much original water as possible. If it needs cleaning, slight or a lot, it should be done gradually over a period of time. A fish's body can only withstand so much stress before illness is imminent. Extreme changes, while not always instantly deadly, can have long term permanent effects, cause damage to vital organs, and at very least will severely weaken the immune system. Once the immune system has been weakened, these fish are vulnerable to every possible illness, disease, and parasite that exists in their world. The stress of moving is extreme enough to cause problems, but when combined with 100% water replacement, a cycling tank because of the water replacement, etc., then the problems can become a bit more complicated and dangerous.
Cichlids in general are not prone to ich. While its not an impossible thing, it is not common except in the situation I just described above. The immune system of most cichlids is quite strong, so the goal for your situation to start with is to get the fish healthy enough to fight the battle using its natural abilities/immune system. With no or low immune system, medications can be quite harsh and often ineffective.
The med ingredient you listed as sodium chloride... that is salt. Too much of a good thing is no good, so adding more salt besides would surely be more than cichlids can handle easily. For this reason I suggested the water changes and halt of any more "medications" or salt.
On to how to get these fish healthy again...
I hate to have to say this, but you are limited to 2 options here. 1. Buy a much larger aquarium asap, or 2. Choose which fish you really desire to keep and part with the rest. That tank is way overcrowded at this point and none of those fish is full grown yet. If you can list for me 3 or 4 fish you really desire to keep, I can help you work out a healthy mix, safe population size, and compatible fish to keep and what should go. The fish I suggest goes first would be the
Goldfish.
Goldfish are very dirty, grow very large and very fast (when healthy) and are cold water fish. All of your other fish are tropical (warm water), so that leaves the
Goldfish in a difficult situation. The new raised temp is not going to do well for that
Goldfish. Warmer water contains less oxygen than cold water, and
Goldfish require/use a large amount of oxygen, more so than most fish species.
Once your population is appropriate for the tank size and amount of filtration, the work of keeping the water chemistry safe and getting it into a healthy state will be much easier and happen much quicker. Once the tank situation is again "healthy", your sick fish will likely heal and be just fine without any further help. If, after the tank is healthy and stable, there is still a problem, I can suggest some safer and more effective medications to use for treatment.
Adding any medication at this point is going to be a no no due to the fluctuations in water chemistry until that tank is fully cycled. Considering the large amount of waste that is going into that water (from the population size and types of fish), I would expect that tank to take quite a bit of time to completely cycle. Decreasing the population now will help speed up the cycling process.
Try as much as possible to avoid stressing the fish further. When you work in/around the tank, move slowly so as not to scare them. Don't try to catch any of them, chase them, etc. Keeping the light off for a while can also help to reduce stress. By all means, make sure the tank has lots and lots of decor in it. Rock work in particular due to the species of fish you are keeping, along with drift wood.
In regards to what water tests you should always have on hand, pH is one of the most important. While many fish can tolerate changes in ammonia, nitrite, nitrate to some degree, pH has a lot less "wiggle room". The fish rely on a stable and appropriate pH level for their organs to function properly. If the pH shifts too much and/or too fast, it can be deadly. Well water, tap water, etc. also will shift in pH during various times of the year. Weather changes, season, pollution, all affect well water. Without the ability to monitor what is in your tank vs what water you are adding, there is no way to control the changes and keep them safe for the fish. So, the basic 4, ammonia, nitrite, nitrate, and pH should be standard kits to keep on hand for any freshwater aquarium. High nitrate levels can affect pH, also. In a situation such as yours, had I been selling you the kits, pH would have been the first one I handed you.
In case you are not aware, API puts out a great master test kit which includes everything you should have on hand. They are accurate (in the top 5 for accuracy), easy to use, and relatively inexpensive (the whole set for under $30). If you need a link to them online, I can provide that for you, please just ask.
Last for this post I wish to mention your filter. Aquaclear 300 is a great filter... however... for that size waste load in a 90 gallon tank, that is not near enough filtration. I would strongly urge you to upgrade your filtration to handle the job for this tank. You have the option of adding to it or replacing it completely. A pair of canister filters could work, but I would be sure to add a small powerhead for circulation. A set of 2 Aqueon 55 filters would work nicely, or even a set of 2 Aquclears (either model 70 or 110 for each, or one of each) would work. The Aquaclear 300 is an older model of the Aquaclear filter, equivalent (if I remember correctly) to the current Aquaclear 30. According to Hagen (the manufacturer), this filter is designed for 10 - 30 gallon tanks that are properly stocked. See the problem? If you need some links to appropriate filters, please ask. I would be more than happy to provide links to the filters I would suggest based on professional experience, personal use, and what would be correct for your situation.
I know this is a lot of information to process, I think I covered everything. I am going to stop now and wait for your reply before we proceed further.
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