It occurred to me that I needed to be more clear about what this meant:
"Get up on the roof at the rear, I betcha the three vents need re-doing (new screens, remove old caulk and re-caulk)."
I meant the three plumbing
vents: all near the rear, 2 on the curbside, 1 on the streetside. They allow your plumbing to drain properly, and if debris, or dead mice or birds are blocking them, they won't work well. Plus, the caulking works itself loose there every few years, and if not attended to, will let water down into your two closets, plus behind the tub/sink area.
You'll need to try somebody like Out-Of-Doors Mart to get the little kits they sell,or make yourself one. There's a rubber gasket made of rubber like an inner tube that has a hole in the middle to pull over the black ABS pipe of the vent, a square piece of screen to stop leaves,bugs, and any other detritus to enter, plus Vulkem caulking. Vulkem has a new name which I can't remember at the moment, but you'll find it.
The vent is all contained in a chromed cast unit about 5"X5" at the base (guessing on the measurement) and it's held on by Phillips head screws. Not a difficult job to do, but an important one, part of the Battle Against Water Ingress!
You'll be up on the roof doing this, so if you have time, use the same Vulkem, and go check around the seams of the three air vents, to make sure that they aren't going to leak on you either. In fact, everything that pierces the roof is a potential threat, and needs to be inspected.
And lastly, always remember: no silicon caulking on the exterior! It is heck* to get off after it goes black (which it always seems to do), and it actually attacks aluminum. The only area you are instructed to use it is on the seams of the bathtub.
*Heck is for those who don't believe in Gosh