What were the results of the last one you took to the lab?
I would give them a call and see if they can run a fecal for worms and coccidiosis.
http://waddl.vetmed.wsu.edu/search-tests If I'm reading it correctly testing is $10.00. Of course that doesn't include your gas money to get there
Having moisture and mud could possibly be a contributing factor. The poop looks like it has a lot of mucous.
If he is failing/declining, then you could try treating for Coccidiosis (Corid), but he may also have some type of infection. The blue/purple comb is indicative that he is not getting enough oxygen. I suppose a severe overload could impact breathing, but infection is more likely.
Do you have access to any antibiotics?
O.k. you mention "when he was eating"? Has he stopped eating and drinking? For how long?
I know it's hard, but do what you can to get some fluids into him. Once he is hydrated, then see if he will eat a little for you. Try some egg or tuna if he doesn't want to eat his normal feed.