Tear drop growth rate

[DustyBoy]

Hey guys, i have a question about the growth rate on a pair of baby tear drop plants. i have had them for about 2 1/2 months now anre they are not growing as fast as i thought they would. Im going with a carpet effect but they dont seem to be spreading like i was thinking. are they a sloooooooow growing plant? I have T8's on them 8 hours a day with water changes at least once a week, about 1 1/2gal per shot, dry ferts about 30 drops per day and im runing CO2 2 drops per sec. I also have the Root Doctor tablets under my sub strait. I also have a crab in there, could he be munching on my plants? any information helps, i want a very green heavly planted tank.