Scours is caused by bacteria such as E-coli, not from pellets. Pellets have everything a rabbit needs in the proper balance. That is why you feed a MEASURED amount. Feeding hay will lower their overall protein intake, but the crux of the matter is the kits gut PH is changing in the extreme at weaning to handle the new diet, and when they stop nursing are no longer protected by the doe's milk and a substance known as "milk oil". One needs to make sure that the cage is very clean and dry . Kits like to sit in their food dishes and will contaminate them, so food needs to be measured out (not free fed) and dishes washed daily. Poop and wet feed etc. also attract flies and other vermin which may also carry disease as well.