All my plants have there 2nd set of leaves growing (there 4th leaves) except for one, my tallest plant wont grow its 4th leaf, it just has 3 and its bigger then the rest and seems to have a good growth rate (i just caught it almost touching one of my CFLs.. stupid plant, but unlike the other ones it only has 3 leaves.. even my plant 1/4 of the size has its 4th leaf, can any1 explain why this is happening?