Not putting on weight

Clarence is eating like a horse but hes so skinny you can feel all his bones He also drinks quite alot of water hes fine in himself very lively etc

My girl bunny Flo is also like this, I have taken her to the vet about it but they found nothing of concern, she is currently on a course of Panacur as recommended by the vet so if no improvement after this then I'll be taking her back! I'm feeding unlimited meadow hay, readigrass (handful a day), dry herbs and 10 pellets each per bun per day. As an occasional treat they get curly kale, cabbage, broccoli or carrot but in small amounts! Oh and the vets recommend half a weetabix a day which I'm feeding! Any advice or reassurance would be greatly appreciated!

Any ideas anyone? :wave: