Acne also arises from E2 fluctuation. Not necessarily just elevated E2. The addition of Primo could have caused a dip in serum estradiol levels that also results in acne flaring up. Acne isn't going to dissipate instantly just bc e2 is not high anymore.
** Give it some time, keep E2 in range & stable, and keep good hygiene! **
15 pg/ml is a bit low and will diminish your gains. E2 is a primary driver of growth.
I'd lower the primo or raise the test dosage. (not both at the same time since ur already having acne issues)
Best of Luck.