Coolant leak on W2 heads

Due to poor weather the last month and landscaping work around home my Dart has not turned a wheel in over a month and a half.

Recently I noticed a small spot under car on passenger side, it was coolant, enough to make a spot 2"x2" over 2 days. I crawled under and found coolant leaking down from exhaust flange area, and head to block around cylinder 8. I wiped it all and cleaned thoroughly and monitored. Dry for several days, then randomly wet at bottom of head again although not enough to drip.

I haven't had a chance to really dig into yet but I did pull rear most header bolt and it is dry. This has me stumped, the car has been on road 2 years with no leaks, engine was dynoed 3 years ago. Why random leak now? As I said car has not moved or even been started in month and a half.

I plan to loosen header and check there although I dont recal W2 heads having wet holes like standard LA. Perhaps the unused set of exhaust bolt holes are leaking???? Surely a head gasket doesnt randomly start leaking???? The weather has been very cool and damp, car is in garage. I'm considering firing it up and seeing if a few heat cycles will stop the issue. The coolant is Evan's.

Thoughts.........