If your negative is coming out thin and low in contrast, you might want to increase your development time by 20% and see what happens.
I saw your second example, but I see the image is out of foucs and looks like your subject moved as well. Without knowing what color the clothing was, it's kind of hard to judge the contrast - but I do see the hair rendered pretty white and the sweater with good density. I also see that scene may have been back lit with not much light going to the face. It may just be a bad example. Do you have another?
By the way, Arista Premium films are Kodak Tri-X and Plus-X. I use them and they are just fine...
OH, yeah... WELCOME TO APUG!