Hi Sean, I am here per request to offer some input and hopefully what seems to be some much needed help. Please bear with me as there are a number of questions I need to ask.
First question will require you to take a very close look at the fish with the swollen abdomen... look from many different angles, do the scales appear to be lifting, such as a pine cone effect?
Is this fish still eating normally?
Can you please provide a list of water params including ammonia, nitrite, nitrate, new pH reading to check stability?
How big of a tank are these fish in?
Tankmates? How many fish total of each species in this tank?
When was this tank set up?
What kind of filtration are you running on this tank? What media in the filter(s)?
What kind of substrate? Decor? Can you offer a pic of the entire tank even if its not real clear?
Live plants? If so, species please.
What foods are you offering and how often?
Maintenance schedule? (water changes, gravel vacs, etc)
How long has the fish with the swollen abdomen been this way? How long did it take to happen? Was it like this when you brought it home?
Ok, now to address some of the other questions you've asked throughout this thread (yes, I have read the entire thread, lol)
Altering the pH of your tap water can be very dangerous for any fish, but there are some methods that are safer than others. The most dangerous would be the use of chemical buffers. These buffers do not come with the appropriate warnings on them and can cause major shifts in pH with no warning. Keeping the water chemistry stable with chemical buffers requires extreme amounts of care, time, testing, and attention, not to mention an expensive supply of chemicals that once started will need to be used for the life of that tank to maintain stability (unless you start over completely). Mixing chemical buffers with other methods of water softening such as drift wood, peat moss, etc. is a no no.
The safest method to soften water is to work with an RO unit, as you have been considering. Provided the membranes remain maintained and changed frequent enough, RO water will offer the stability that the chemicals do not. With RO water mixed to tap water you can control exactly where your pH will fall when you mix, and thus can control at all times what is going into the tank. Increase or decrease of RO water and a good accurate test kit will help you to adjust the ratio of RO to tap to meet your tank needs.
Peat moss, Welaby wood, Malaysian drift wood... all "natural" buffers, but with one draw back... there is no level of control, thus stability can go down the toilet if you don't watch things carefully enough, test often enough, increase/decrease the amount of these used, and perform often enough water changes to attempt to maintain the stability fish such as rams require.
Of all the contributions so far in this thread, the one that stands out for me the most is the one from Byron about where the fish have come from. Be persistent with the lfs, let them know that if they don't provide you the information needed to keep these fish safely and healthy, then you are going to hold them responsible for the loss of these fish. Don't be afraid to stand up, and if need be, find a new lfs to shop in the future. Blue and gold rams alike are very sensitive to change, but how do you know what is change for them if you don't first know what they came from? Other questions you should be asking the lfs is how long they were in the store before you purchased them and what the tank parameters are for the store tanks. Knowing where they came from is vital, but the lfs is one of the places they came from, so you need all of that info to make informed decisions and to get a clear picture of what these fish have been through. If they have already suffered extreme changes from breeder to store, and then again in your tank, this changes protocol for how to treat them now vs if the breeder and store have the same parameters, or your water and the store have the same parameters, etc. Knowing the general time from of what they've been exposed to also helps.
I have kept rams that required soft water, but I have also kept rams that required hard water. The hard water fish were bred and raised in a pH of 7.8 - 8.0, which was the same as my tap water at that time. Of an entire shipment of 50 rams, my pair were the only survivors, simply because I took them home before they were acclimated to the store tank, which had soft water... because everyone knows that rams need soft water, right? This is how my boss figured out that these were tank raised fish and why he had lost over 100 of them over the course of 2 wks. Once he learned that my 2 were the only survivors I suggested he call the breeder and check on water params, and it turned out they were raised in Florida with fairly hard water. The same applies in reverse, all dependent on where they were raised.
At this time I would suggest making no new changes, but rather maintain what you have been currently doing with/for them. Once I have the info I need I can then better advise you on how to safely proceed, and hopefully we can also help the apparently sick fish. (the swollen belly as in the photo is not normal)
I will check in a few times over the course of today/tonight to look for your reply, as I can see this is an urgent matter and needs to be taken care of asap. If something new happens between now and then, please include that in your reply. If you are seeking a quicker response, pm me and ask me to check on the thread. I get notified via email of any pm's I receive, thus I am more likely to see it faster and get back her sooner to help.
Hang in there...