Tray? You're developing sheet film? If so, I'll bet the spots that look like pinholes are actually caused by dust on the film when it's exposed.(posted 8909 days ago)Take a sheet straight out of the box, expose it to light and process it and see if you get the same thing. That'll give you the answer.
I really can't imagine ordinary stop after Ilfosol-S causing pinholes with HP5+.