Should I be concerned about minor cracks in the corners of some upstairs rooms? ?

Question

There is a slight dirty water color around the cracks. Also, next to the exhaust fan on the bathroom ceiling is a 6 inch dirty water stain. And there are 2 long hairline cracks there as well.

Answer 1

Yup, you should be VERY concerned.  Sounds like you have water leaking in around the flashing (is the flashing even there?) around the fan in your bathroom.  Water is getting in, traveling, causing mold and rot.

You had better nip this in the rear right away, before the repairs become REALLY expensive!

~Garnet

Permaculture homesteading/farming over 20 years

Doing our own repairs on our houses, and barns for years.

Answer 2

You have water coming in from your vents when it rains from a certain direction.   If you are seeing the damage on the drywall, it has leaked enough that it has soaked through the insulation as well.

You really should have it addressed by someone who can work on roofs when you can.