Yes, it could be the enzymes. Try stopping those.
The most common food allergens are beef, chicken, lamb, wheat, corn, soy, and dairy. You will want to avoid all of those.
The only truly hypo-allergenic food out there is hills z/d. The protein molecules have be hydrolyzed to make them so small that the body does not recognize them. Because the body can not recognize the protein molecules, the body can not have an allergic reaction. So, it may be helpful to try the z/d diet
. You have to get it from a vet.
If he is allergic to chicken, then there is a good chance he is allergic to duck. Or he soon will be.
Usually what you are describing, where it is on multiple sites on the body with no skin lesions or itching, is caused by what they are taking by mouth or eating.
So, stop the enzymes. If the odor does not clear up in a week then I would try putting him on hills z/d.