@johnpoz Thanks again for your help and input!
Wanted to give an update:
I did receive my 16-port Unifi Switch Lite 16, swapped it in and moved some switches around. Doing so, I was able to take out two Ubiquiti Edge Router X's (in VLAN Switch mode) and a simply unmanaged switch. Now the only brand of switch I am using is Unifi switches.
After taking out the Edgerouters, things started to work as expected. I'm very familiar with the Unifi switches, but a little less so with the Edgerouters. Despite my best attempts to set them up properly with the correct VID's and PVID's for my different VLANS, ports, and trunks downstream from my primary switch, I must have still gotten something wrong and been creating some sort of STP issue.
As I said, now that I am using only Unifi switches, things are working as expected, so we seem to be all clear! Thanks again for all of your help and input!