The UVB shouldn't be a problem for a while, I didn't have mine for the first few weeks, and my turtle survived

. It's probably a good idea to gradually raise the water level, I did that as well. If anything it made me feel better and let the turtle adjust gradually, especially if one is weak. It may be a good idea to add a floating plant for them to rest on, that way if they get tired when swimming they have a pit stop.
Also, cute names for the turtles, i like them.