You don't. You feed everyone a flock or grower feed with oyster shells available for your girls. Layer feed, more often than not, is lackluster. Nutritionally speaking.
Shouldn't, sorry. Autocorrect. Rosters, cockerels, chicks, nonlaying pullets and nonlaying hens should not eat layer. Calcium is too high. Just give the vitamins orally or mix it into their feed.
Roosters and birds that are currently nor laying should really be eating layer feed. I'm not sure if it's his issue, I'd try treating him for vitamin deficiency.
400 i.u vitamin E capsule and a third of b complex tablet every day for a few weeks. Any brand from the grocery store in fine.