Matt....could you post up your training regimen? Workouts/sets/reps?
I have a theory. I know diet is 70% of your results, and I won't tell you your diet sucks because I've seen pics of your meal prep and whatnot and it actually looks pretty solid. But From what I've seen in the last couple years with your threads it seems your training is not conducive to hypertrophy. You seem to be most concerned with physique rather than strength but your videos and what I've heard tell me your training is more strength oriented. Heavy deadlifts for 2 reps, setting PR's on bench for 1-3 reps, etc. Your muscles are pretty firm and dense, which is normal for strength trainers, but I think you'll get more size from a routine more revolved around hypertrophy. Less weight, more reps, strict form, TUT, etc.
I started really growing when I swallowed my ego and dropped all my lifts and focused on all the important factors for growth. Plus my joints feel much better as well.