A short post toady with some logical advise that many people will fail to adhere to.
“If a muscle isn’t growing you’re either at your genetic limit or more likely not hitting the required overload/intensity.”
What does this mean? Simply that you need to train all of your muscles with the correct stimulus and intensity to create the required metallic disturbance for them to adapt and grow bigger/stronger. If you’re not doing that you won’t grow, it’s that simple. A caloric surplus of 350-500cals per day over your TDEE will help as well, but the most important part is the stimulus.
Overload is king.