That could be what's doing it but how can you say that it is definately doing it with out even knowing the setup Greenstick???? You don't even know what he is using for fertilizer. Conerned, post the full details of your setup so we can help you diagnose and fix that problem of yours. Soil, fertilizers used, pot size, watering cycle, grow enviroment, temps, lighting, etc. List as much info as you have and it will make it easier for people to figure out the problem.