My son is on the same boat. I’ve started juicing and incorporating broccoli sprouts in the juice. Because he’s a picky eater I use a syringe and hold his nose so he swallows it. I kid you not this past month has been an explosion of words, we call him a parrot. Definitely believe the lack of nutrients can contribute but that’s just my opinion and experience ☺️
Has he been referred for speech therapy yet?