If they just started you can most likely fix it. Start bigger and more frequent water changes, get some Vitachem, and upgrade the filtration when you can.
What's are your tank parameters with your water change schedule right now? Do you have sand or gravel i cant tell from the picture? Also throw some pothos plants in there. When my seam popped on my 265 and I had to put all the fish in the 300 gallon so its really overstocked and some of my bass started to develop issues looked to be the start of hith so I checked my water params and nitrates were high. I increased to 3x 140 gallon water changes weekly and siphon gravel once a week. Cleared up all issues luckily for me, Nitrates are around 20ppm with the increased water change schedule. I also don't feed on water change days I feed twice a day on non water change days bio gold for breakfast and hikari sticks and massivore for dinner. I also give them treats once a week mainly tilapia and shrimp maybe I should start soaking the treats in vitachem as suggested. Not sure if this will help you Shelby.
I haven't checked nitrates in a while to be honest. I do have gravel and I siphon it once a week. My water change is once a week as well. Im going to step that up to twice. 40% each time. Also gonna feed every other day for a while. I will check my nitrate levels tonight for curiosity. I have some snooks in there taking up water quality that I might ditch as well. Thanks Cigars