Your landing dock shouldn't be sinking. Keep the dock afloat where the turtle(s) can completely dry off themselves. The basking dock should be about 10 degrees higher than the water's temp. And I won't say anything about trout chow because I haven't heard such thing to feed the turtles. Maybe someone else can give some information about that.
Also if you have more than one turtle, a 55 gallon sounds a bit small.