I have two northern leopard frog tadpoles. I've had them for just a little over a month. I've noticed that one of them is WAY smaller and has developed a lump on the side of its tail. They were about the same size when they arrived? Is the smaller one sick? Has anyone had any experience with a lump on the tail? And yes, I feed them regularly, their water is changed twice a week and dechlorinated. I do not handle them at all.
Here are some pictures. They were just in the cup while I changed the water in their tank.

http://imgur.com/gallery/TbE4psP