Yes, my son eats very well too, we were very much into good food and DS had a very varied diet, obviously nothing prepared me for the shock of having to change our diet completely to accommodate for DS allergies (egg, soya, dairy, fish, nuts, peanuts, sesame, kiwi, shell fish, bananas, tomatoes, and wheat).
I have learned a lot about how ingredients interact chemically with each other just trying to get a cake to raise (and this extended to all of his food). We did quite a lot of research to ensure he continued having a healthy variety of foods, it was a lot of work but it was well worth it, DS was a different child a few weeks after the allergens were removed from his diet.
Fingers crossed he is not allergic, but if he is, mumsnet has been a god send in terms of tips, recipes, and support. I hope you find it as useful as I have. 