U7 Pro abysmal performance

As the title states, I am getting impressively poor performance across all of my wireless devices. I installed a second U7 in the garage recently (foolishly thinking it might help) and performance has gotten even worse. Opened a support ticket and I'm getting frustrated at the response times from support.

I love all my other Ubiquiti equipment, but sub Mbps speeds and >300ms latency while standing underneath an AP is just unsatisfactory.

Has anyone else experienced these issues and if you found a resolution, what was it?

Update:
I was on travel while everyone replied (thank you for all the suggestions!).

I went through and tried nearly all of them. I was mostly already in alignment with what was suggested.

What seems to have worked (At least for now), was to remove both AP's from the network, readopt, optimize channels.

FWIW, I'm running 4 SSID/VLANs (IoT2.4+Guest2.4/5+TV2.4/5+Secure2.4/5/6)
Fast Roaming off
Minimum RSSI off