Header exhaust leak - help!

I've had this set of Dougs for about a year now, first on the LA heads and more recently on the 308's (non magnum). The heads were match ported , shaved and polished. Never a problem until recently. Not sure why the flanges would arch being it they sat on a shelf for 3 months while my motor was being built.

I do think its worth pulling them off again to see if there's a high or low spot. I'll take a closer look at the Percy's but may go with the Remflex. I like the idea of running a thicker gasket.

I appreciate all the feedback.

Would the gold zinc stuff do any good or just burn off? Sucks that its weeping just enough on the top to really get my attention!