Gray tank leaking from top or side?

I'm pretty sure my trailer's primary gray tank (under the bathroom for the shower and sink) is leaking. Once the tank is about half full steadily drips down the side and off the bottom of the tank. I attached some photos below that show what I see.

I first noticed the issue last year at one of our first camping trips after buying the trailer, and thought my shower drain was leaking through the floor and water was collecting (then later leaking down) from the top of the gray tank and then running off. Well let me rephrase... my shower drain WAS leaking and I fixed that with some new plumber's putty & re-tightened the drain to the shower floor. But this last weekend the underbody dripping began again.

When I get underneath the trailer and eyeball the tank, it (the tank) really seems squeezed in tight between support beams. Could one of those beams have rubbed through the surface of the tank and caused a puncture? I can't really see any way to inspect this and find the leak without removing the entire tank. I'm not sure if that is a worthwhile endeavor or not, for a fairly slow leak of "clean" gray water.

Anyone ever dealt with this sort of issue?