Losing pressure at the tap

Hey there.
I have a 140 foot well with fracture at about 120, 6gpm when drilled (20 years ago).
Lately I've been losing pressure at the tap - especially when I run more than one tap at a time. Prior to this I have been able to run multiple taps (hose, kitchen, washing machine etc) at once but not anymore!
What's up? Is it my pressure tank, the pump, the well, the pumptec?

Any opinions or advice are appreciated!

Take it easy! and thanks!

Any filters?

Yeah!
Pretty recently installed UV with a big white cylinder that I'll check right now!
I hope that's it, didn't think about it. You think it could make that much difference?

Speedbump, you're my new hero! Stinky, iron-filled, slimy filter cartridge in that blue plastic case. We've been on the well for 10 years but the filtration is only 12 months old...Significantly longer than the recommended filter lifespan, I reckon.
Doh!

I would leave the cartridge out. That's all it's really doing is dropping your pressure. Those things don't filter enough of anything to do an ounce of good. The only type of filter that is worth anything for household use backwashes regularilly.