Ideas on what's causing my click/tick/rattle noise?

I got the pistons cleaned up last night using the parts washer, a toothbrush sized wire brush, and LOTS of elbow grease. I ran out of elbow grease before I ran out of crud, but they are way cleaner. Here are the "after" photos, in order from 1-6. There is no pitting at all on the tops, just the factory machining marks.

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