Happened on my standard Edelbrock heads with Erson rockers many years back with a reasonably aggressive Lunati solid flat tappet. I put it down to to over revving (lots of 6000's, quite a few 6500's and the occasional zip to 7000, then the valve springs really gave up & I couldn't hit 6!). I covered everything with a shop towel, left individual tips poking through, dressed them with an angle grinder and ran lash caps. They were fine thereafter for many years until the heads came off for a rebuild. Ran lash caps since as I don't think the tips were hardened very well.