Leo hasn't been basking, as far as I know, for about 2 weeks now!!

I lowered his water temp to between 76-78 (it had been 80- he's still a baby) and filled the water up a bit higher so the basking light would be closer to the dock in hopes of enticing (sp) him to the warmth! I've had that same basking light since I first got him, is there a possibility it may be getting weaker and becoming less warm for him? Other then not basking as much, he seems perfectly fine. He eats well (pellets and romaine), defecates regularly, and is very active!
???