I think you're good. A similar thing happened to me last year. I had ACA insurance (no subsidy) though September and went on my wife's insurance in October. I thought the ACA insurance would cancel if you didn't pay your premium since you pay it monthly in advance. Turns out you actually have to cancel it through the exchange. I called CareFirst and they said they couldn't revoke my coverage for the month of October because they are required by law to follow what the exchange tells them and the exchange said I still had coverage. However, CareFirst wouldn't pay any claims in October since I hadn't paid the premium. I was okay with that because I now had insurance through my wife's job. I confirmed with CareFirst that the unpaid premium wouldn't generate a collections notice or prohibit me from using CarsFirst in the future. They said it wouldn't. They're not paying claims since no premium was paid so they didn't really care.
I did with a huge ClusterF because eventually UnitedHealthcare learned that I technically already had insurance for the month of October through CareFirst so UH not my primary insurer for that month. I thought they were so there was a couple months of hassle having my October claims rejected and then resubmitted to CF, which we're then denid, and resubmitted again through UH as a secondary insurer. UH even went so far as to claw back a payment made for a doctor visit, deny the claim resubmittal as the primary insurer, them approve and repay the claim later as the secondary insurer (since it was denied through my primary insurer due to lack of premium payment). You may not have this issue since your insurers are in different states but it might not hurt to check if you have claims during the overlapping month.