molly weird

My only male molly fish that lives in a 20-gallon with 2 small shrimp, a few small snails, a bristle nose pleco, 3 female mollies (two of which are his daughters), 2 male guppies, 4 baby mollies, and 6 tetras. Around 2 weeks ago I saw him sitting at the bottom of the tank barely moving. The day...