Tmax is probably the most available and finest grain film. With Tmax 100, you can get a nearly grainless image. I processed it with D76 and XTOL and didn't see much difference in results.
I don't know how long ago your neg was made but if it was a long time ago, it is quite possible the formulation may have changed. You might want to try a new roll and if you still feel a need to change. With Tri-X, a roll from 30 years ago look nothing like one from today.