Probably environmental. I'd give him some benedryl(1mg per #of the dog) and natural vitamin C(citrus bioflavanoids or EsterC). Start at 500mg of the C and over a week up it to 1000/ split between meals. Then the next week give 2000mg daily again split it between meals. C is a natural antihistimine and anti inflammatory. Also supports the immune system. Coconut oil may be better than the fish oil or rotate them. I'd also give some local honey with a good plain organic yogurt(probiotic). The honey may help if it is environmental allergies. Do you even have 'local' honey in the key's?
Where I am, lack of humidity is the problem, but you may be dealing with trapped moisture in the coat so causes some irritation. Keep an eye on that, maybe some gold bond medicated powder will help if that is the problem.