If you are wondering whether they have worms, you should consider worming them, as it's a safe bet that chickens will get SOME worms. There are some pieces in that pic that look a bit like rice, small short white pieces, and this could be an indication of tapeworm. You could see if your vet will do a test on the poop to check for worms -- many will, and it is usually not expensive. Most wormers don't treat tapeworms. I'll give you a couple of links, to hopefully help you decide your next step.