Sorry for your loss. It is always best to know what the problem is before throwing a lot of treatments at chickens. Acidified copper sulfate is sometimes use to treat canker when antibiotic metronidazole is not available, and for sour crop in some cases. It is not something I would use when I had an unknown disease because it can be overdosed or misused. The is cooper sulfate and acidified copper sulfate. Only the latter should ever be used.
The first dropping has some normal cecal poop and regular poop, but a lot of mucus and urates. Has either one had diarrhea?
I’m sorry that you lost your little rooster. Did you vet check for coccidiosis and worms, and rule those out? A lot of white urates can indicate dehydration in a sick bird. Green poop indicates not eating enough. The best way to find out if there is a disease or something contagious is to have your state vet do a necropsy by taking in or sending the bird in on a weekday. The body should be cold but not frozen. Here is a list of most state vets to contact:
https://www.metzerfarms.com/poultry-labs.html