Unhappy Tortoises?

Hi,

I've had my turtles for at least 6 years and I got one and then another about a year later. They live in a glass tank about 2.5 by 4 feet I think and they have a coconut bark type of floorings with a large shoe box with sides cut (w/out a lid of course) for a house. They only seem to eat lettuce and they have a heater (when it's winter and cold spring and cold autumn) and a lamp that imitates the sun (gives them sunlight). I feed them and to be honest I try to keep it at a constant time and I try to bathe them when I can (They are clean and well kept trust me!!!!), but I don't like to take them outside when its warm because every time they literally go in different directions and I've almost lost them sometimes! Basically my question is, how can I make my tortoises happy? because most of the time I feel as if I'm just making them unhappy and that if they weren't domesticated they would be happy and not sad. It might seem weird, but I feel like I could do more and I don't know if it's normal or not! they don't like to get wet and just poop in the little pool I put into their tank and it was impossible for me to keep clean. I just need some tips to make them happy and healthy in their tank!!!! Thanks for reading through this long letter of me just rambling