Too many supplements. Could I have vitamin C allergy?

Yes .You are right ! Vitamins in nature(fruits, vegetables, egg yoke, sauerkraut, fish, ...) exist in several isomers each of them. That means their molecule looking completely differently in space and all of them go together.That is very very expensive to produce commercially and does not happen.That's why you can not have the wanted benefit. Eat organic foods. Smaller amounts of the natural vitamins have huge effect.