If they are on the ground they probably have worms. If you are able to get a fecal float done by your vet on a fresh morning collective sample, you can find out what worms are present. I used to believe that giving pumpkin seeds and cayenne pepper would keep chickens from getting worms, but I found out that it won't treat an infestation. I like to use natural remedies if they work, but I learned that treatments like fenbendazole (SafeGuard liquid goat wormer, Panacur) and Valbazen were very safe and much better for chickens than having worms. Many people treat twice a year with 1/2 ml of either of those.