you could have also just plateaued. have you tried changing up the exercises in your routine? changing the order too? what is your on-off schedule? if you do back and chest on the same day usually, switch it up and do back and triceps the same day. if you did bicep and tricep on one day, do bicep and chest that day. change up the order of the workouts.
are you doing heavy weight with low reps, or light weight with high reps? heavy weight low reps is really good for bulking on the muscle. be careful with that though. a lot of people try to do more weight than their body can handle and end up using more momentum and their back and end up hurting themselves. you don't want to be "that guy" at the gym. the one who is curling 75 lbs dumbells, but is just swinging his arms, back and whole body to just throw the dumbell up. not using his bicep at all.
my protein shake intake i take syntha6/myofusion (whichever is on sale when i buy it) for breakfast and before bed. they have a nice slow release of protein over the course of a few hours. your muscles are going to do a lot of repairing when you're asleep, so it's good to have that nice shot of protein (i have a small bladder, so it keeps me up

). then i have whey for lunch, dinner, and post workouts. taking just protein for your meals and post workouts isn't always enough, gotta start distributing it better. should probably bring it up to 200g of protein too.