This is a slow external coolant leak from the head gasket as you suspect - weather or not it has slowed or stopped on its own ( which in my experience is very unlikely ) . the condition of the gasket as a whole and what is occuring internally on the head sealing surface is a function of the condition of the gasket as manifested by this external leak. So the upshot is I would definitely pull the head and replace the gasket. I will warrant that you will find a well eroded head gasket. I hope this helps - let me know if you need anything else.

regards