Unfortunately, my first post is a cry for help.
I have a 6 foot tank housing discus, various plecs three of which are zebras, corys and tetras.
On Saturday whilst carrying out a partial water change I noticed a zebra plec fry on the side of the tank (about 1.2cms).

The thin fish died two days later, now one of the others is on its back, also looking thin

Have put in a bit of coco nut shell for security.
Any ideas what has gone wrong? I felt I had no choice but to move them into the hatchery.
If I come across any more fry should I leave them to nature and hope there are enough hiding places in the tank.
Any suggestions would be greatly appreciated.