Yes, I've had runny poop when the flock eats "chick starter". They're on a layer feed now but it could be a treat issue. They were given old broccoli, kale, and Brussel sprouts. Not moldy or spoiled, but not in its prime. Perhaps my portions given were too generous....I thought my birds had worms. It turned out I was just giving them too much protein treats. Sunflower seeds and mealworms. I cut back on the protein and poop return to normal. Not certain its your issue, just what I've come across.
Added... also I remember someone saying occasionally added food grade DTE to their feed to deworming them.