Hi mpenzi.
A limp body and no breathing often follows a tonic-clonic (or grand mal) seizure. The turning blue is from lack of oxygen. Usually, a person will begin breathing again after a few seconds (~10 in my wife's case) but it is always a scary period.
There are a few diets that kids and adults can try (ketogenic, modified atkins, low glycemic, etc.), but I don't know how applicable (or safe) they might be for a 6 month old.