Rattle then lost cylinder

[Judpie]

Hi guys, my 2010 ve sv6 started to get a rattle ( sounded like a quick fan sort of rattle, and sounded like coming out near speaker in middle of dash). This rattle came at high rpm (4-5k) especially in second. Today I was testing it to see if rattle still there and check engine light came on and it dropped a cylinder. There were no ‘limp mode’ or any other warnings. It still drove with dropped cylinder but then 10 minutes later check light went off and it drove normal. Any ideas? Petrol? Coils, sparks? Thanks in advance