Start by navigating to the Issues tab in the feed tool and then scrolling down to product issues:
Note that Product Issues must be imported if they are not currently populated as they are cached for only 4 days. Click Import Product Issues and wait 5-10mins and then refresh your browser:
If you know the specific attribute affected by a particular issues you can filter for it under Attribute Name. For example, if you have a number of issues for missing gtin you can filter for that:
Additionally, you can click on the actual link for the error description to further filter out for specific issues. When filtering for specific issues, you can then choose to remove entire subsets of affected products by clicking Remove Products:
Do note that this remove products from your Master Feed Control thus affecting all channels.
After removing products, you should resend your feed to force a recrawl by a channel like Google.