What is this?

[Thatspec]

Pretty sure I know but I'd be interested in some better informed opinions. I've been using white vinegar at about 1/4 or 5 for stop bath, is this what's meant by "pinholes"?

 

[ath]

No, it's dirt on the film. Maybe silver particles from very old fixer.
Pinholes would be black when viewed as positive.

 

[rodinal]

Ditto what Andreas says.
Try filtering your fixer with a paper coffee filter at the beginning of your developing session, even if not that old.

Marcelo

 

[Thatspec]

Thanks guys, I will try filtering the fixer. Makes sense as it was not on all frames though only 1/3 of that fixer had been used for one roll and poured back into the remaining 2/3. Made with distilled water too.