We recently discovered a leak manifesting itself with stains in our ceiling. It likely happened a few days ago when we had about 2-3" of rain overnight. We have never had a leak before, and the roof itself was installed 6 years with new sheathing. Since our solar panels are mounted close to the affected spot, my initial hunch was that the leak was from a roof penetration, but upon inspection I am unsure if that is the culprit. Because the rafters are old and have prior moisture marks, I can't determine the exact spot of the water penetration into the attic.
I do see that there is a visible gap between two sheathing OSB pieces where the one piece of rafter meets another, and the second piece is a bit higher (see photo #1 below). This manifested by a slight depression or dip in shingles above (photo #2). This is the general area of the leak (within a foot or so) but I am unable to see any gaps or issues with the shingles, so what should the procedure be to fix this issue? Should we run a hose and find the spot? And for the fix, should we just "unlock" shingles in the general area and apply sealant?
Note: There are no water pipes, HVAC or other water related stuff in the attic.