Natural supplements isn't going to help.Add Apple Cider to its water. This is good to do all the time, but will especially help now to give your rooster a boost. https://www.tractorsupply.com/tsc/p...bCbbwyQ_fS9Ai1OIfj64_R16XaE8OlqIaAqSDEALw_wcB
This link is great for keeping mites and parasites out of the coop and off of the chickens. YOu can either dust the chickens' feathers and skin with this or sprinkle lots in the run and coop for when they take dust baths. This is very important and is maybe what your rooster has. If parasites are not treated quickly it may lead to anemia.
It may be spring and your chicken is getting lots of pollen in its respiratory system. This may lead to respiratory issues and can sometimes cause a purple comb. I recommend cleaning out your coop. Though there is really nothing you can do with the pollen, airing out the dust from their coop is very helpful. Make sure to keep a clean coop.
Just for extra health, I recommend adding garlic and turmeric to their feed for a little while. This will help with anti-inflammatory, immune health, and antibacterial.
Blood flow supplements:
https://www.tractorsupply.com/tsc/p...6kh_-c8BazZlCovV97Ng1slVlpybGeI0aAgXgEALw_wcB
https://www.tractorsupply.com/tsc/p...hYFQUtnxGAbnnJByz1ueOhk_gpbe8xFAaAqh0EALw_wcB
Respiratory health supplements:
https://www.tractorsupply.com/tsc/p...fqb1fLO4Ei3Isx-wdBiN8F-vbQgOHn8saAnzREALw_wcB
What happened to tagging me to help others?