hi i have a problem my plants are only 2 weeks old the 1st 7 days they grew like wild fire got to about 15 cm in the first week so i put the lights on and now they have just stopped growing they only have 2 leafs and they are really small the 2 round leafs have curled up, but the leafs are still nice and green what can i do im useing hed lights and am growin in my cupboard its quiet cool in there could this be the problem not enough heat but then they grew perfectly for the 1st week and a couple of days after that but then they just completely stopped please help