The OP said the hens are acting normally, not lethargic. To me, that indicated Coccidiosis Is not the problem. Chickens with Coccidiosis don’t always poop bloody stools, but they do act lethargic.
It won’t do any harm to treat with Corid, just observe the withdrawal period for eating the...
Mine eat a lot of tomatoes during the season without that happening. I seriously doubt it was tomatoes. The beet skins made a difference and I've seen a blue sheen on the poop from them eating red cabbage so food is a possibility. But no, not tomatoes.
Judy makes a good point on looking...
Some possibilities:
One time I was certain I saw blood in the coop and run. This bright red splashed on the ground and on some wood. The chickens looked fine, no problem at all. I was mystified, then remembered I’d canned beets the day before and given them the cooked skins. What have you...