I don’t recommend feeding them anything, to be honest with you. The rabbits are wild, and as such will need to learn to fend for themselves. Feeding them could hinder that process, and cause a lot of issues for them down the road. It’s best to let them be.

As for knowing what their gender is, the only way is to look underneath them. I don’t actually know what to look for, I had to have my vet do it for me. But there are no visible signs that tell the genders apart without looking down there.