Sick Zebra

[clueless]

Hi just wondering if any body has had fish deform on them my tank is healthy all water tests are spot on but one of my zebras and now two platys are starting to look deformed the zebra has a bloated tummy and the tail has twisted the other two zebras are sleek and fit and they all seem healthy and are swimming fine two small platys have also started to get a deformed tail but not the bloated tummy
any body any ideas

thanks clueless

 

[bigfish]

are they eating?

could be internal worms

 

[clueless]

Yes eating fine swimming fine fins heathy just dont look right noticed a bit of flicking off rocks from a couple of other fish but not from them