Likewise, if you're running your APs in Solo/Standalone mode, reboot the one closest to your LAN router.
A Solo AP upon boot will run a SmartSelect algorithm and pick the least congested/occupied channel at that time. [But all three could see the same results, because w/o controller they don't communicate]
Then lock down the 2.4 Ghz channel that it picked, 1/6/11, and *manually* set your other APs to the other two channels.
This will reduce co-channel interference, and should provide best coverage/data rates.
After a short period, look at your AP channel choices for 5G, and I'd suggest locking them down to different channels too.
Please let us know if this helps?