The small bruises you see are indeed from the firing pin tips. This is caused by the tumblers being out of time and not retracting back into the frame soon enough/quickly enough to clear the extractor as it moves up when the gun is opened.
It might be prudent to inspect the firing pin tips to make sure they are not dangerously deformed from this, which could lead to a pierced primer. If the tips are OK, simply "opening up" the deformed area very slightly for added clearance may be all that's needed.
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