So I have this 35g tank and my 2 platys keep hiding at the bottom of the tank and laying down on the gravel. All the other fish are fine and are acting normally. The water is fine and all the other fish are too. Why are they hiding so much (with their belly touching the ground)? I never paid attention to their genders and now I cant find our cause they are hiding. Also I've never seen them mating so I'm not sure whats wrong with them.