My Silkie Rooster was having similar symptoms about 5 weeks ago. When his limp became worse and he was laying more than standing, I took him to a farm Vet. The Dr. Checked his stool and there was no Cocci. or parasites. He did see more bacteria than normal, so he gave him an antibiotic inj. (gave me the second dose to give 3 days later) and gave him B12 and steroid inj. My roo seemed a bit better, 1-2 days afterwards, but then back to laying around. He progressively got worse, unable to stand. After reading online, I suspected Marek’s disease (no cure and contagious to chickens. My Vet agreed and I had the Vet. put him to sleep. It broke my heart, as he and another Silkie hen were my 1st chickens since 1 day old. He was only 1 1/2 yr old. There is a vaccination for Marek’s but it has to be given within 24 hrs. of hatching.
Hopefully your roo doesn’t have Marek’s, but do separate him, regardless. Best of luck to you and your roo!