I highly recommend you read this it will answer your questions. https://www.backyardchickens.com/articles/coccidiosis-prevention-cure-and-natural-healing.64404/ It has great info too.
Definitely post pics. Chickens will shed intestinal lining which will look like blood. My chick did it and I was very worried it was coccidiosis but then it turned out to just be intestine stuff. Do you have other chickens? I wouldn't continue with the greens until you know exactly what this is.