Lethargic, 7 week old chick

[Dorking Dork]

I have a 7 week old Buff Brahma roo who was lethargic and drowsy, 2 weeks ago. I treated with egg yolk, sugar water, and Corid. He recovered after 24 hours, 2 weeks ago. Then, he began showing the same, lethargic, drowsy symptoms a week later. I’ve treated with the same thing, egg yolk, sugar water, and Corid for 7 days and see no sign of improvement this time. He was supposedly vaccinated for coccidiosis and Mareks from the hatchery. However, I made a mistake in feeding medicated feed. I switched to non-medicated feed a week ago. He is with 5 other healthy chicks. What is going on and what more can I do?

 

[Dorking Dork]

Now I am suspecting wry neck? Roo is turning head almost upside down and laying on the floor sprawled out. I bought some “Rooster Booster” to shock supplement vitamins and selenium. Hoping for improvement but so far, none, 10 hours after first dose was given. Any more ideas? I really would not like to lose this chick. Daughter is very attached