The Arista.Ultra EDU films are all a little bit slow compared to their rated box speed, regardless of developer. You may wish to try exposing them at about half box speed for more solid shadow detail, and clearer details in those areas.
I found the ISO 100 to work well at EI 50, the ISO 200 well at EI 80, and the ISO 400 well at EI 160. If you use a speed enhancing developer, such as TMax or Ilfotec DD-X, you may get a bit more.
I hope that helps! Beautiful portrait.