A switch in email services crashed our domain reputation, any advice?

Hello, I've run into an issue lately with my marketing emails. For experimenting we paused mailchimp (for marketing mails) and used Amazon SES for marketing mails. We started sending around 30K per week from the same sender (noreply@domain.co) and then our domain reputation for our domain went to "BAD" from "LOW" in google postmaster tool, now all our (non marketing) mails (even from Gsuite) is landing in the recipient's spam folder, we have stopped SES and returned to mailchimp for marketing mails, but our domain reputation hasn't increased as of now.
We suspected the issue is from our configuration. When we were using amazon ses at that time DKIM was properly setup but not the other 2, not sure why, attaching screenshot of gmail postmaster tool for the same. But now we have set everything up attaching screenshots.

Any insights can help us a ton in this situation, thank you!