DNS lookup painfully slow on only one network? I've got a MacBook Air 2013 running 10.14, and loading all pages either stalls for multiple seconds on "Resolving host" and only loads after a painful delay or it completely fails and Chrome shows me a "Could not resolve DNS error." This is consistent across browsers, so I'm inclined to believe this is an OS issue. 

What's throwing me for a loop is: this only happens on one network! The router has a 2.4Ghz and a 5Ghz network, and they both have this problem. The only way I can use the internet without tearing my hair out is to tether to my phone. 

Any ideas? Maybe I have a forgotten DNS setup that only fails on this router/ISP combo and I need to reset my DNS settings?
Thanks for all the suggestions. I verified that this is indeed only a problem on this machine, so I figured it must be something misconfigured. 

I found that I had Cloudflare's 1.1.1.1 (and associated backup and IPV6 addresses) as manually-set DNS servers for only this network. When I removed these addresses, my lookups became blazingly fast. 

The mystery is now: why is 1.1.1.1 so slow? I set these as my DNS servers on my iPhone and it's nice and fast. I'll mark this question as solved because my original question has been resolved, but it have generated another bigger question.