One of my matamata just died. And the other ones suddenly stopped feeding. The seem to have stiff legs and one keeps putting his head above the water, instead of just his nose, and keeps his mouth wide open. The tank seems to be clean. PH is 5.0.
Can anybody help? I don't know what to do.....Can it be the fish (guppies) the ate the last week? Some have died, although most seem to be alright.

