I've got a flowerbed next to my pool (borders the shell). I noticed recently that it was staying most in one corner, so I excavated and found that the (outside of the) shell itself was moist. In trying to diagnose the root cause of this moisture (which I think also may explain a few tiles that popped loose), I noticed that several of my coping stones have become separated from the pool shell and there is now a decent gap between the two (see link to picture below). I am assuming that water gets splashed into these gaps and then wets the shell, gradually causing the bond between the two to fail.
My question is, how should I deal with this issue? Should I just caulk the gap with some silicon, or do I need to put something in the gap (under the coping) too? Do I need to do something more substantial, like removing the stones and having them reattached (new thinset?)? Could I caulk now and then come back with something more permanent (expensive) if the stones actually come loose?
The pool is ~12 years old. We just moved in at the end of last Summer. Is this typical wear and tear or a sign of something worse?
Thanks for the help!