My Tomato Plant is Yellow/not growing

[cbs1507]

I planted 4 tomato plants (I'm not sure of the variety) a earlier this month on the same day. I begin to notice something wierd about one the plants a couple weeks ago. I tried taking off the lower limb/leaves, but that didn't seem to help. I tried to research and found out that tomato plants can be determinate/indeterminate. I have no idea which one, but it says don't prune determinate, so as the days have been passing I have just left it alone. The plant has become yellowish, and hasn't grown at all. However, I don't notice any wilting thus far. I have no idea what this could be. My other plants are faring much better, especially the one to the far right which already has a flower bud. Does anybody know what could be the problem?

Here is the plants on May 21:

s157.photobucket.com/user/cbs1507/slideshow/Tomato%20Plants%202014/May%2021_%202014

May 30 (this morning):

s157.photobucket.com/user/cbs1507/slideshow/Tomato%20Plants%202014/May%2030_%202014

As you can see the yellow plant is far shorter than the others. Does anybody know what's causing this?