So 3 weeks ago you replaced your crankset, cassette, and chain.
Obviously you will need clean the rear derailleur and jockey wheels. Lube then jockey wheel inner bearing surfaces and re-assemble.
But now is a good time to make a decision if you want to continue with a wet chain lube or go to a dry chain lube. If you are not going to clean the drivetrain on a regular basis, a dry lube runs cleaner. You usually have to re-apply more often, but you avoid the buildup.
John