2tsp of corid, my rooster had bad blood diarrhea and was treating the whole flock and he is just now having normal poops but now shes acting funky.
Vitamin E and Selenium are used to treat symptoms of Wry Neck (neurological symptoms).I was thinking along the lines of vitamin deficiency. Shes eating and drinking just less than she usually does. Ive just given her some selenium and vitamin E gel.
I would take care not to give too much Selenium, it can be toxic if overdone. Feed contains Selenium. A bit of egg daily would provide sufficient Selenium as well. Vitamin E should be at least 400IU daily.
Vitamin B2 (Riboflavin) is usually given as therapy for legs.
Corid is given for 5-7 days. Blood in the poop can be caused by Coccidiosis, but enteritis could be a contributor as well. Getting a fecal float to see if there is an overload of Coccidia still would be a good idea. Could be the rooster (cockerel?) isn't drinking enough of the mixed water. If the blood continues I would give him a direct oral dose of liquid Corid at a rate of 0.10ml per pound of weight once a day for 3 days - this is in addition to him drinking his fill of Corid water daily too.
Highly unlikely 2 weeks of Corid is causing the leg issues (vitamin deficiency), it's mild and acts as a B1 (Thiamine) mimicker to help reduce the number of oocysts so the bird can build resistance.
I'm sorry you're having trouble, hopefully you will see improvement.