I can add to your list. This is just what I have on that battle. I agree with you that they most likely were all captured.
54th nc--5th Maine
6th nc---5th Maine
8th La---6th Maine (You have that one).
Total: 5th Maine (4 flags)
6th Maine (1 flag)
121st ny (2 flags)
Grand Total: Seven flags captured.
Would the regimental histories help on this issue? I saw a regimental book for the 121st new york on Ebay. Would they list flags they captured at battles?
Have a good morning,