Actually, yes, you are forgetting quite a bit. I can't quite tell if those are desert tortoises or sulcatas, but it doesn't matter, because the aquarium is way too small for one of them, let alone three. Please read the care sheet that is pinned at the top of our sulcata section (same care as desert tortoises) and make some drastic changes: A bigger habitat, a substrate you can moisten, a separate enclosure for each tortoise, two hiding places per tortoise, a tile to feed on and a plant saucer for water, a UVB light, a CHE for night time heat and a cuttlebone.
Tortoises are not herd type animals. They don't co-exist with other tortoises. Rather, they fight to keep other tortoises out of their territory. It is very stressful to have more than one tortoise in one enclosure, and there is no way for the weaker one to get away from the stronger one.
Oh, and the food. Iceburg lettuce has minimal nutrients. It is mostly water. If you want your tortoises to grow and be healthy, you'll need to feed them a better diet. It's all in the care sheet.
I don't mean to be a bubble-buster, but that enclosure is not going to cut it for one tortoise...let alone three. Please follow Yvonne's advice and ask lots of questions. We are here to help and I'm glad that you were brave enough to post that photo, that means that you want to do the best you can for your torts and I can only wish that everyone out there was like that. Check this link out for lots of good reading: http://www.tortoiseforum.org/forums/sulcata-tortoises.88/
I forgot to mention that tortoises with aberrant scute patterns are a favorite of mine, so that one in the middle is very attractive to me. I'd like to see more pictures of it. Very nice, indeed!!!