No water upstairs without downstairs tap

I have an odd problem, the taps in my upstairs bathroom randomly stop giving water, if i open the taps nothing happens. If i go downstairs and turn on the tap it will start slow for 1 second then go normal and i hear the upstairs tap kick in.
This seems to happen mornings after water has not been used overnight.

This started happening a few days ago. The water pressure tank gauge shows about 27-28 psi constantly. (Technically the gauge is on the main water line a few inches from the tank, not on it... unsure if thats proper or not. When i knock on it it sounds empty.

Suggestions appreciated.

Probably have so much elevation to the upstairs that the pressure won't drop low enough to start the pump until you open a lower faucet. Turn the pressure switch up to at least 30/50.

now when this happens the downstairs tap also has low pressure for the first second before it kicks in, is that ok?
also.. very noob question. where do I find the pressure switch?

Thank you!

The pressure switch is the little grey or black box on the tank with all the wires coming out of it. Don't mess with the small adjustment screw. Just tighten the large adjustment screw about two full turns to the right and give it a try.

TURN POWER OFF FIRST!!

is it this fellow? (i didnt take the cover off, it was like that when I bought the house a few months ago)

Wow! That maybe your whole problem. You should get a new one. The nipple that it screws onto may also be clogged.