I looked at Alliant's website and noticed that you are following their recommendations using 4.4gr for a 124gr projectile which is a good start.
I think you should consider shrinking your OAL. 1.68" is The maximum OAL specified by SAAMI. Notice on Alliant's recommendation for Bullseye they are indicating a OAL of 1.12".
As your OAL decreases, the pressure inside your case will increase and will result in a higher velocity without using any additional powder.
Long OAL's (like yours) could be contributing to less pressure and velocity than you are expecting. Try reloading a batch at 1.16", 1.14", 1.12" and keep an eye out for pressure signs along the way. You could also go a bit shorter than that if you feel comfortable. Most people I know have OAL's between 1.09" and 1.12" when using 124gr in 9mm.
I also highly suggest buying a chronograph. It will help you troubleshoot what is going on with your loads and help you find that perfect balance of OAL, powder, and velocity that works best for you.