The water quality in that tank is not up to par. 2 of the fish are showing fin rot and a third has the beginnings of it. Yes the 2 with the fin rot do look stunted. But will look better with regular water changes. Looks like 5 in the tank. How big are they. What are you ready to do to get them back to health? If the 3 big ones are over 5” they’d be at least $75 a piece the smaller if 4” probably about $50.