What disease was this?

[33ChickenLovers]

(Not important information)
So quite awhile back I had this Plymouth Rock named David. He had a twin brother called Samson. They were about 4 months old. We got them fit and healthy.

(important information)
Then 2 months pass (they are now about maybe 6 months old) Samson is flourishing and looking fabulous and started to crow etc. Meanwhile, David has gone down hill. Looks the same as when we got him except a lot more week and pale.
Then in a few days he starts gasping. Then his comb/wattle day by day got purplish. 2 months later, I go out to collect eggs and he’s inside the coop as usual. Only this time he’s twitching like crazy so I pick him up and just hug him, as I know there’s nothing else I can do. Then yes he dies.
Please tell me, what was wrong with him? (His diet was seed, and I did give him medicine just can’t remember what it was.)

 

[CluckerFamily]

Was his diet seed or feed?

 

[Swbertrand1]

An all seed diet is not really enough nutrition for adult birds. Why did you give "medicine"? What ailed him to give medicine?

Back to feed. If you've got hens, a layer feed is a good choice for them, but really doesn't address the rooster(s). If you've got roosters, an "all-flock" feed might be better with some additional calcium offered on the side for the hens. Here's an article that might explain it a little better:
https://backyardpoultry.iamcountryside.com/feed-health/are-you-wondering-what-do-roosters-eat/