Does the tank have an overflow that diverts water to a sump? If not, how high do you keep the water? If the water is to high it can wick over and between the trim. If the silicone that holds the trim on only has a gap in that corner, it may be showing itself over there. If you have a reef ready with overflow and it's still doing that, then chances are the water level is not to high and yeah, bad things afoot.
Hopefully you can find it and it isn't a leak.