The only change I think I made in that time period was I changed all networks except my guest network to the same name and password to let each individual device connect to the best network per it's specs.

My AT&T gateway speed test still shows I'm getting around the 1G service as expected, and prior to making the change described above my speed tests in the Deco app were showing similar #'s.

So I'm wondering if my changes really caused a drop or are the readings just misleading?