Im losing water

I opened my pool yesterday. It held the water over the winter. I drained it just below the return. I filled it up and over night it drained back down to just below the skimmer. I am thinking i have a leak in the skimmer.

THe gasket for the widemouth faceplate has been replace 2 years ago when i replaced the liner. I am wondering if maybe the other gasket is bad. It looks old and dry rotted. I was going to take it apart but couldnt get it apart. If that is the problem do i need to replace the whole skimmer?

I was thinking so. I posted in another post asking for a good skimmer to get because I may just go that route anyway.

What do you guys think?

Have you tried dye testing the skimmer? Before replacing the skimmer, I'd make sure that it is the problem.