tuna fish maybe...corn..., it sounds like you already have quiet the array of things available for them...i hope they start to put some weight on for you.. Their poops are solid and look "normal"?...not watery?... I am just taking a guess here...i don't know much about Barred rocks..although I REALLY like them...I would say the lighter of the two is the cockerel..and the darker the pullet..hahaha, or...the opposite..or both are the same sex..

..sorry, i had to do it.. the leg color on the lighter one is really nice and yellow....wish my girls(wyandottes) had that color on their legs..but, they are laying and that makes things dull-down a little sometimes..:/