You should get a sulfer burner.
I think your clone is getting old. But I also think even a new OG Kush clone would burn easy. It's just a trait of the strain. It was a freak of chemdawg. So it had to be stablized from a mistake. So I think that is why it is so sensitive. I think you can get those seeds at rezivour seeds. I'll get the link.
They do have an IBL of Sour Diesel. Get it quick before they shut down there site like everyone else.