We’re getting 503 error on your site, and then the memory error. Please contact your hosting provider support to check if there are any issues on a server.
Why do you think the problem is caused by our theme?
A lot of customers use XStore without the problem, it looks like the problem is caused by something on the server-side or by 3rd party plugin you are using.
Let us know the answer of your hosting provider.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.