good questions..also please tell us your specific workout schedule, and how much time you actually spend in the gym....also how much cardio do you do?
no more than 2 hours of training.
I can't running & no doing cardio,because of my low back problem since 25s years ago.
now with injured knee problem...
Just try no rest and higher reps during workout.and KEEP A LOW FAT,almost NO SALT diet all year around.