Routing issues in my area

I've been having connection issues since Tuesday night. All the speed tests I run show full speed (over 400 Mbps down, 40 up) but some sites like Yahoo load very slowly while other like Youtube seem fine. Other examples: iTunes (via the Windows app) won't download any podcasts for me. They start but never get past about 5%. I have a Proton VPN account but it's connection is so slow (since Tuesday) that every site I try connecting through it is slow. I've rebooted my modem and router but that had no effect. There's also a Nextdoor thread running in my neighborhood with many others reporting the same issue so I don't think it's me. It seems to be a routing issue with certain web sites and not others. Even this forum page loaded pretty slow.