@hteezy With the limited info provided, the advice can only get so specific so here are some questions:
Have you gradually increased base calories over the 10 months to account for a higher TDEE?
You mentioned protein but are you eating lots of good juicy carbs? Were you eating lots of carbs but are now eating less? Have you made any other dietary changes, specifically sodium related in the last 4 months?
I saw nsuns mentioned somewhere in this thread. Have you tried a program more suited for hypertrophy?
Related to that - Have you tried increasing volume for your arms? Adding extra sets, movements, or a dedicated arm day?
How long have you been training? For most people, 6 months is probably as long as you want to run a dedicated bulk. At a certain point, the size gains just aint going to be what they were at the beginning of the bulk. May be a good time to move to maintenance or cut and let your body get ready for another bulk in the near future.
Forgive me if I'm wrong but I'm gonna guess you're fairly young, in both actual and training age. If I'm right, just hang in there. Growth comes in spurts; sometimes you feel like you're going nowhere and then boom! it hits you like a sack of potatoes.