D.B.
There is an awesome children's supplement available in vanilla and chocolate that supplies a huge amount of essential nutrients in a highly absorbable form. It's called Reliv Now for Kids and it's available from distributors, and it has a 30 day money back guarantee. Plus the nutritional consultant will help you figure out ways to disguise it in different recipes to vary it for picky eaters. It has DHA for brain development and, for many kids, it's all they get (especially in 3rd world feeding stations). Even a little bit will help allay your fears while he either comes out of this phase or you figure out what else is going on. It's totally safe, no warning labels like kids' vitamins (!) and is given to preemies in feeding tubes in hospitals, given to failure-to-thrive kids, and so on. Happy to help you more!