If you are letting the soil dry before watering then i'd say that its nute burn, mg soil is too hot for marijuana. I use westlands/west plus and even that is pretty hot. The leaves look dry and scorched, unable to transpire water probably from too much heat or too many nutes in the soil. I wouldn't fertilise mg soil until the plants tell me too as it seems to have enough nutrients for the bulk of the grow. Try finding a website called 'Mandalla Seeds' it explains soil growing better than i ever could, the grow guide is at the bottom of the home page. A question to 'Dj Ruiner' - your plants look great but you have some degree of purpling on the leaf stems, could this be from the soil nutes stressing them a bit? One of your plants is totally green though all over though, what soil do you use??
