Looks to be what my Navy friends would refer to as FOD *
Foreign object damage. *
You'd be amazed at how junk can migrate from cylinder to cylinder , but hitting them all means there were many pieces floating around.
If there are no sharp edges , my next worry would be stress risers where a crack would start.
A little delicate work with a cartridge roll and have them inspected for cracks. I got a kit years back that was three aerosol cans.....cleaner , dye and developer that worked really well on aluminum......but you'll want to get them as clean as possible first.