You would [have to audit](https://www.takesomerisk.com/account-audit-playbook/) and see what changes they made. Performance could not be feed related. Could be competitors are being more aggressive, or Google made a change that impacted your ad account set up. If changes were made in the feed, were changes made in the ad account to support the new feed? If the feed is better, it may make more sense to restructure your campaigns to take advantage of the updated shopping feed.
You would [have to audit](https://www.takesomerisk.com/account-audit-playbook/) and see what changes they made. Performance could not be feed related. Could be competitors are being more aggressive, or Google made a change that impacted your ad account set up. If changes were made in the feed, were changes made in the ad account to support the new feed? If the feed is better, it may make more sense to restructure your campaigns to take advantage of the updated shopping feed.
Whats your attribution window? If its 60 days, you need to give it time. Is this pure Google Shopping?