
He could have had a reaction to the detergent ingredient in the shampoo you used - Tea Tree shampoos are not made of that alone ;)
The fact that his skin has broken out suddenly but
particularly that he is obviously very down / depressed, personally I'd visit the vet rather than try and second guess what's wrong. Take the shampoo with you in case there is anything on the ingredient list which helps the vet identify whether it's the most likely cause. Have a think about if you've changed any household cleaners, detergents, fabrics etc recently too.
Skin conditions can be food based - I see you offer him a very restricted ingredient intake which is presumably because you've discovered he has intolerances to several things. If that's the case I'm not sue about the tripe sticks - they're usually beef tripe I think and beef is often on the list of dietary no-go foods for allergy prone dogs. As an aside, rather than adding CLO to his diet I would change that to fish body oil.
HTH, regards Teri