Posted: Sat Jan 23, 2010 3:00 pm
I'm very sorry for your loss.
Where did you buy them? If you got them from some kind of market or a pet store that kept them in crowded, substandard conditions, one could have been ill when you bought them---symptoms sometimes don't show up until a turtle is really sick or worse. Their underdeveloped immune systems can make them more susceptible to illness and bacteria; the stress of shipping and conditions they were kept in even prior to wherever you bought them from could have contributed. Or, it could even have been something congenital. It's really hard to know what went wrong if the turtle was acting healthy and they had a good set-up like you say.
Don't feel sorry for the one turtle and be tempted to get a companion. The 10-gallon tank is actually better for one hatchling than two. And the turtle will not be lonely, especially if you give the attention you say you do. I would, however, do a good cleaning of the tank and objects in it just in case whatever the one had is contagious.
Regarding the diet---stop the shrimp, except for the very occasional treat (you must know it's really high in protein and as the staple makes for a very unbalanced diet). I don't know what you're using for pellets, but get some Reptomin Baby (made for smaller turtles and has a bit more calcium in it than most pellets). If your RES is so small that the pellet is difficult to eat, break it into smaller pieces. I'd skip tubifex worms---they're often unclean. As for carrots, I've found that turtles, especially smaller ones, are more tempted to nibble on them when they're offered as thin, small worm-like peels. Aside from the plants, try some pieces of red-leaf lettuce in the tank.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-