Use the tech that you're most familiar with so that you can concentrate on solving your customers' problems. Only introduce tech that you're unfamiliar with if that solves a problem you can't solve with your existing knowledge. A new company is hard work and any opportunity to make something easier should be grabbed with both hands.
At the same time, it's easy to burn out on the problems of your business. If hacking on new tech is something you enjoy as a hobby, you should schedule downtime for yourself and do some experimenting (preferably nothing related to your business). At the very least you'll come back mentally refreshed, and if you're lucky you might find a new perspective to solve an existing problem in your business. I wouldn't advise doing this if you don't consider learning new tech as recreation though.