Mucus in the mouth of my rooster

[owlbaby]

I noticed my serama rooster, Abbott, yesterday...., in the morning he was fine, came out of the coop with the gang and was running around but when I got home I noticed he was off to the side and acting very lethargic. When I picked him up I noticed quite a bit of mucus in his mouth. I have since isolated him, and given him some yogurt, ACV, water and some scrambled eggs which he did not touch. I actually fed him with a syringe the ACV, water and yogurt combo. I have attached pics, his comb seems to be a little darker on the edges....

Is there anything else I should do for him, take him to the vet, get some antibiotics, I am picking up VET RX tomorrow, I have coconut oil.
Thanks for any help, he is my sweetie, he was one of my first hatchlings!

 

[MysteryChicken]

@Eggcessive

 

[Eggcessive]

Can you look inside his beak for yellow plaques or cankers? I would clean off the yellow mucus with a wet cloth. Is there a bad odor from his face or beak? Is he sneezing or having drainage from his nostrils?

 

[ackie]

My roo that got beaten up and is healing quite nicely has occasionally had mucus or slimy spit in his beak as well. Following this thread.

 

[owlbaby]

No cankers, and no mucus from his nose but one eye is runny. I got some of the the mucus out of his mouth but it is pretty hard and he is 'eating' my concoction: yogurt, ACV, and water!