My 5 year old Pelusios Castaneus very rarely enters the water. Matter of fact, she eats on the basking area and when she's hungry, she sticks her head in the water. On average, she takes a quick swim once a month!
I see nothing wrong with your turtles and extended basking is nothing to worry about.
Sidenecks like to walk around on the bottom thus I am against raising the water level. Matter of fact, I would lower it! They like an environment similar to Soft shells.
Either way, your turtle does not need a vet.