Q about Nute Sticky

I was just reading through the Nutrient Sticky put together by BobBong (thanks for that, by the way :thumbsup:) and noticed something. This may sound like an obvious question to many growers, but all of these symptoms of deficiency only apply to established plants with alternating nodes, completely in the vegetative state, right? I notice a lot of questions about what to do about yellowing of the Cotelydons or having a purple stem, which seem to be common seedling characteristics that don't require any action. I also notice a lot of beginners trying to solve those "problems" by using nutrients, which is not safe for such young plants. Unless I'm missing something and there are actually specific problems with seedlings that can be resolved with nutrients. Thanks for the Sticky and thanks for any advice. :jointsmile: