SOHO Mk3 “dropping” of 5GHz devices

New SOHO Mk3 user here running 8.1.2. My 5 GHz devices are getting dropped constantly. The 2.4 GHz side seems to be Ok as far as I can tell. The only device that’s using that is an IOT type device. Everything else I have is running on 5 GHz. I’ve made several adjustments to the 5 GHz side (trying fixed and auto channel) to no avail. Where I notice this is on the family iPhones (latest iOS updates). I’m running Max Boost power and still seems weak to the point I’m considering an AP One Mini AC.

Any ideas. Thanks for your help!