Continue the Corid as instructed above. How are all the chicks acting?
If any have symptoms more than the bloody droppings it would be a good idea to also give those ones an oral dose
in addition to the medicated water. If any are not eating or drinking well, seem lethargic or sleepy, or are sitting fluffed up, then I would add the oral dose to treatment. Dosing for that is here:
https://www.backyardchickens.com/threads/corid-oral-drench-instructions.1211991/
Corid is very safe, very little risk of overdosing, so if in doubt treating is the right thing to do.