Not old leaves new leaves healthy leaves from on top in middle. They seem to like certain plants more. Its not the fish pretty sure. If there is no algae or I don't give any special food for the shrimps could they be eating the plants. This happens with lights are out at night. I've been going in and checking periodically through out the night. All fish are sleeping. But shrimps are out in about. I been eliminating snails out of my tank. There are no significant snails left but maybe tiny tiny ones. And when I see them I smash them. But since the snails are just about 98% gone the plant eating has continued with seems even more now. The fish are Otos, SAE , CAE BN plecos. I have all those same fish in another tank but no shrimps or snails and no plants are getting eaten.