I see you’re using Windows as a server too.
It’s a know inssue that the default server parameters are not optimal in Windows in some cases.
To fix it, a new version 0.12.2 is being released next week. This version, instead of using the same parameters for all the servers, will automatically change those parameters according to the memory the server has.
As you are already using 0.12.1, you can upgrade it because features wise nothing changes with the new version. I hope it will be released on Monday, or Tuesday at most.
If you can’t wait I can give you instructions to put the needed parameter manually (I would need to know how much RAM your server has). If you can wait for the next week, it would be better as you won’t need to touch any config file.