Ok so I have a 30 gallon tank and I have a big problem I stated my tank with a 3 black strip damsel then I got a Yellow-tail Blue Damsel at first the two fought and the striped on got beat up and looked bad but I gave it like a week and he was fine. So then the other day I bought a clown fish and 4 red leg crabs and my striped damsel started looking really bad like pale and just did barrel rows when he swam and so last night he died sad yea I know well when I got home today the clownfish was at the front top of the tank on his side then went a like laid on the bottom but started swimming again but like slow and stuff and the yellow tailed damsel is really really pale and he usually is active but he’s just sitting there so does anyone know what’s wrong with my tank plzz help me fix this problem helpppppppppppppppppppp me save my fish