Bathroom fixture dimmed, then power out at all 5 fixtures

[alpentolic]

Hello and thank you. I had a main bathroom fixture start a delay after flipping the switch, and coming on dim.

After a couple days, none of the wired bathroom fixtures had power in either of my 2 bathrooms; 4 lights and 1 fan. The outlets still worked fine.

There is a GFCI feeding the bathroom outlets located in my garage. It tested fine but I replaced it anyway. I can't tell if it also is supposed to feed the fixtures but I assume so? The panel switch works fine.

I pulled the fixtures and tested for any power, checked the wire nuts and whatever connections I could reach. Nothing looked loose or corroded. I could not detect any power to any of the hot wires on any fixture.

I climbed into the attic but was in over my head with all the insulation blown around. I traced the romex as far as I could but again didn't see anything that looked damaged.

The only thing that looked like it could be a problem is the back bathroom fan which sits right over the shower. The wiring did not look bad but there was alot of crud all over in the opening.

attached is my crude diagram of where these fixtures are located. The bottom right light fixture in the pic is the one that dimmed and delayed before they all went out.

Thanks again for any advice or help.