White spots on negs

I've read pretty mch everything I can find to get rid of the tiny
white spots on my b&w negs but nothing seems to help. They are only
visible in prints or scans from the negs.

I live in a very hard water area so I'm assuming it's particles in the
water causing it. For my lastest attempt, I used distilled water in
the final rinse and tap water for everything else (ilford say not to
mix chemicals with distilled water) and there was no improvement at
all. This leads me to believe the particles in the water are stopping
development under them rather than drying in the wet film. Should I
try distilled water for everything? Filtered water?

The darkroom I use (the universities) has a "not drinking water" sign
over the sink. Dunno if this means anything.

This problem is driving me nuts! The negs are perfect otherwise. Any
help appreciated.