I'm playing on the Nutaku server and using Chrome browser, but not experiencing any delays at all. Not sure about mobile, but for pc, clearing complete browser history, from beginning of time, might help.

Also, I suggest using Chrome when playing games on Nutaku. Nutaku even states that their games work best using the Chrome browser. The latest Firefox Quantum browser update is junk, imo, and has caused me problems in all kinds of browser games. I play all browser games in Chrome now, not just the ones from Nutaku.