About 5 week ago I noticed a 'shiny' white and silver/grey patch on one of my clown loaches that spanned most of one side of his body. My nitrates were reading a little high (around 60ppm) so I did several large water changes until they were down to 20ppm. The patch did not go away and one of my other clowns started to show a similar much smaller patch so I started treating with Paraguard. I just finished treating the tank for 10 days and also did 3 x 1.5 hour baths in the higher concentration of the solution. About a week ago I noticed that my 8 inch synodontis nigriventris started showing small patches and had sort of 'cloudy' eyes. He also has some white on where the two parts of his body meet (sorry, I don't know how to better explain it, see the attached photo) and has became more reclusive (especially after doing the Paraguard baths). The patches on him are small and don't show on camera and I can't say for certain if the are just nicks or something more sinister.
Over the course of the last few days I have started to notice symptoms on all 5 of my clown loaches. They are all quite young and about 1.5-2.5 inches in length. The weird thing is that the symptoms seem to vary from fish to fish. Some have that large shiny patch, others have duller, smaller white patches on their heads, a few have fins that a starting to deteriorate (no fuzz, just bits missing) and now I've noticed two have otherwise healthy looking fins with stringy white material coming off them (although it is quite short so no sure if it's fungus or a parasite). All the loaches show good color and seem to be active and eating, but I'm worried as whatever they have seems to be getting worse and has been unaffected by Paraguard.
Below are my tank details:
50 gallon freshwater tank (5x2" clown loaches, 1x8" synodontis nigriventris, 1x5" Chinese algae eater, 3 x 1" white cloud minnow).
Tank has been set up for about 2 months.
Using a Filstar XP M canister filter (carbon removed due to Paraguard treatment)
Typically do 20% water change/grave vacuum weekly, have not done on in the last 10 days due to Paraguard treatment.
I am thinking that I need to treat with an antibiotic? Should I be using Maracyn, Maracyn-2 or something else? Any advice on what I should do next would be greatly appreciated! I would really like to save these fish.