PHP Version changed by Plesk on subdomain

Hello,

I have following contruct:
primarydomain.de
- PHP 5.4
dev.primarydomain.de
- PHP 5.5

Sometimes, if I change something (not php-related) on primarydomain.de, the php version from this domain is set automatically to the subdomain. THis is not on every change. I don't know which action calls this behavior.

Plesk version 12.5.30 Update #23,

This is for Plesk on Linux, sorry I posted wrong. Maybe someone can move it?

Alex