i have two common plecos at about 3 and 4.5 inches respectively, and both have fairly ragged fins with significant splits in them. i changed the water and added fungus clear as a precaution, but no visible signs of infection exist, and part of it could be due to nipping from tankmates. will they ever grow back healthy again?
I have 4 three spot gouramis in the tank but they are all quite docile and mind their own business. When the plecos were much smaller I had a large gold gourami in the tank that picked on EVERYONE and chewed up the plecos bad all the time...quite the bad attitude. then one day the plecos decided they had enough of his abuse and ate him. and i was never exactly sure how that worked out...
Does it look like anything is nipping their fins? Have you seen them get picked on? Or are they just ragged? It could be your substrate which is tearing up their fins. They spend a lot of time squirming around on the underside of decorations scraping across the substrate.
I have a pleco whose fins were ragged in a tank with somewhat sharp pebbles. I moved him to a tank with play sand, and they grew back in really nicely.