I just went through the same thing with my 05 Southwind.
When I looked the first time I didn't see the crack in my skylight but the second time on the roof I did. I went up with a tube of caulk to make a temporary repair until I got home to fix it right. When I touched the skylight it shattered!
I had to make some emergency repairs to seal up the hole to get home and finish my vacation.
When I got home I had my local RV shop replace both skylights and reseal the roof, They went over all joints and roof cuts, such as the AC units and plumbing vents. They did a real nice job and I've had no problems since!
Do yourself a favor and just replace the skylights,,, sooner or later they will shatter!
05 Southwind 37C