Less FPS after overclocking, what to do?

I recently overclocked my GPU, but since I only found out later that my CPU was the problem and not the GPU, I reset it. But the next day the FPS had dropped sharply. In simple games like KovaaK I only have 90-100 instead of 250-300 FPS. Have already looked with Afterburner, there my CPU is overloaded, but before that it had managed to double / triple (but only dropped so much in Kovaak and 3Dmark, in other games like Fortnite only 20-30 FPS). What could be the problem? Can't scrap through overclocking the GPU, can it?

Just uninstall the OC tools used for overclocking, e.g. The "MSI Afterburner", then restart Windows and then look again at the FPS in your games.

Ok, I'll give it a try.