RDS Aurora Postgres Instance Memory Usage Fluctuating

Running a RDS Aurora Postgres cluster with two r6g.2xlarge instances that started fluctuating in memory usage around 6:50pm EST yesterday. Typically we are running with ~16gb headroom but it dips to ~5gb at ~10m intervals. At some points it dipped below the threshold that it needed to restart the instance. We rolled back any code changes that had happened during the day

How can I see which process/query is using this memory?

Noticed this corresponded very closely to the announcement of performance insights.