White specs on leaves

Me again...
Hate to seem like that noob who's always asking for advice, I've got a handful of grows under my belt and have managed them fine, seem to be having alot of issues with this one.

I've had a few issues which I think I've sorted now and the plants are on the road to recovery. Wrong ph bad ventilation and heat stress.
However something that's concerning me is little white specs over the leaves and if I'm not mistaken, more seem to be appearing on other plants aswell. Is this something to be worried about? I'm hoping they are not little eggs or bugs or whatever, they seem to have just appeared overnight. Anybody recognise this sort of thing?

I would get the spray out just in case

Spray them with what?

Take a close up pic of the underside of some of the worse leaves.

Underside of the worst leaves...seem to look pretty normal?

Ok nothing underneath, i took a screenshot of one of your pics and zoomed in! There is deffo something on them. Any tiny bits coming from the top of your tent or ceiling?? Try shaking the white bits off

It looks like dried salts from foliar feeds or some other residue.