I am very suspicious of that powder you are using.
Unburnt powder will look yellow, sometimes gray, if my memory is correct. I have no idea why you are not getting good combustion. This whole situation makes no sense if you are using the proper powder, primers, and cases.
I would load some 223 shells with a known powder, say IMR 4895, Varget, and see if your AR functions.
If you have a chronograph that will tell if something anomalous, velocity wise, is going on.
Do not “add” more powder in the concept that your charges are low.
If I'm not shooting, I'm reloading.