Can masturbation or early sex stunt my growth?

You don't loose any significant nutrients as you claim when you ejaculate, unless you are breaking some kind of record on the amount of semen you produce. Normal adult semen volume is only a teaspoon, about as much as you spit a couple of times. Semen only has about 100 calories, the measure of energy output. Sounds like you just want to argue the issue and have made your mind up so why even bother asking the question? Every guy i know growing up had solo sex daily at least, and all of them pretty much mirror their dads or brothers in height or are taller. Generally most brothers are similar in size, and if one happened to masturbate a whole lot more than the other, then under your premise one would be much taller than the other. Doesn't happen. Solo sex or masturbation is a natural act by humans and other mammals. We are designed to ejaculate. Enjoy it.