Your prospecting campaigns are designed to find NEW customers — but they're also reaching people who bought from Mira in the last 90 days. You already have a '90-day purchasers' audience built; you just haven't added it to the exclusion list on those campaigns.
The dollar waste is modest (~$480/mo), but the bigger cost is brand experience. Someone who bought your serum last month is now seeing 'try Mira for the first time' ads. The fix is 30 seconds per ad set.