Try using your D-76 straight rather than diluted, and as others have stated, switch to something other than Tri-X. Developers come in different categories, for lack of a better word. Some fall into what is considered a solvent developer (Perceptol for example, although there are many others) - these give smoother tonality especially in areas of large similar tonal values, like skies and skin. Others fall into the category of acutance developers (Rodinal for example) - they give more pronounced apparent grain. Others still, like your D-76 (and ID-11) are considered middle of the road in that regard, neither solvent nor acutance.
Diluting your developer (D-76) moves it toward the acutance end of the spectrum while using it straight tends to move it toward the solvent end, generally speaking. Be advised that apparent grain means a print that has a higher apparent sharpness, again, generally speaking. If you are not happy with the results that you are getting, try using Microdol-X or Perceptol with a 400 speed film, or keep the D-76 and try a film like FP4+ or Plus-X.
Not all films are created equal in this regard. Some films, even those that have the same ASA rating, are just going to have higher apparent grain than others no matter what developer you use, so you may want to consider using a different 400 speed film. What ever you do, change only one thing at a time so that you can tell which change gave you the results that you like. Then you can try keeping that the same and changing something else to see if you can make further improvements, or not.
- Randy
