I would separate those males or you're going to end up with a bunch of seeds in your weed, unless of course that's what you want. It appears that you may be growing different varieties? That would explain the different behaviors. Don't worry about the nute burn if it's only on about 5%, just cut back from now on. I don't know why one leaf would be bigger, except that the older and lower leaves of course are bigger than the younger ones, and again could be a different variety.