No point doing anything, as even if they finished as highest bidder, you can not force them to pay.

The most that would happen is they would get a non payment strike, but any attempt to enforce the contract

would be up to you as a civil matter.  If you did manage to force a sale via ebay, the buyer will simply claim INAD and you will be forced to refund and worse the item you get back might not be in the condition you sold it.

Your best option would be to block the retracted bidders, from any further bidding on your items.