If you don't have a fan circulating the air than you need to do that too....door with cracks in it isn't sufficient enough, plus when you get to the flowering stage all those cracks in there are going to cause light leaks and potentially make your plants hermie......It could be getting nute burn from the MG as they have time released fertilizer that is said to not be good for the plants. I'm not really an expert on problems, as I didn't really run into them in my grow so I'm sure soon enough someone will tell you the true problem...