Something In my #5 Cylinder?

These are CP Carrillo forged Boost spec pistons. Was running 27* of timing during drag week. When I saw signs of detonation I dropped that back to 23*. It seems very happy at 23*. I think I was also running too hot of plugs? During drag week I ran NGK BKRE6-11 plugs which is a 6 heat range. I have since dropped back to a 7 heat range NGK... should I go colder when it all goes back together?