Your definition of heavy is important, but I squat at >80% twice per week and my legs are coming up and I'm not feeling fatigued. Every other week or so I throw in some high volume on the squat, 4 sets of 20 or so, and I think that has played an important role in my improved development. Something worth trying if you haven't before.
I don't think you've got anything to worry about if you're getting sufficient nutrition, rest and recovery. It might be easier to advise you if you gave us a look at a typical workout w/ sets & reps, just because I think people have a tendency to use the word "heavy" a little loosely when it comes to leg day. Also, being on cycle will make recovery a lot quicker.