Express growing with Northern Express

Hello! Over the previous week it had grown enormously, but now it almost stopped. The last two days it stays the same, cones began to shape, and there are first troubles with the lack of nitro, so some leaves are yellow. In the beginning of the week I gave each of them 3 liters of water with PH6, and in a couple of days fed it with fresh compote with a good part of nitro – one liter per plant. It must help.