The turtles need something to climb up on. They do bask out of the water, they still have toes (no flippers), so they do go on land.
You can also try giving them night crawlers or worms (it is messy! lol), I don't know about the musk turtle but I'm aslo assuming that he has little toes and claws that enable him to climb up, give him something to bask on also.
If your BP is 18 inches he needs a larger enclosure. Give him the choice of a cool spot and a warm spot so he doesn't have to chose security over regulating body temps.
Try getting a UTH or human heating pad and put it UNDER the tank. Make sure it does not go over 90-95 degrees. BP's NEED belly heat.
Get rid of the hot rock in your monitors cage. They can cause electrical fires and can easily burn your monitors. They often get burnt before they even realize how hot they are, then it's usually to late.
Neptune, Zion, Enigma,