Multiple php versions = Internal server error.

Hey all,

I want to move a domain and a website from a Direct Admin server to my new Debian 9 server with Virtualmin.
Setting up the virtual server and the domain did’t give my any trouble but the website is made with PHP-fusion 7.
As php-fusion 7 setup has probs with php7 (mysql deprecated), i wanted to install it in an seperate folder within public_html, and enabeling php5.6 for that folder.

I installed php5.6 and did the recheck configuration in virtualmin. Changed the php-version of that folder to 5.6 but now i’m getting ‘Internal Server error’ on all php files in that folder.
I do get these errors in the domains error_log :

[Thu Apr 12 21:08:56.226555 2018] [fcgid:warn] [pid 5224] (104)Connection reset by peer: [client 109.128.144.175:56373] mod_fcgid: error reading data from FastCGI server
[Thu Apr 12 21:08:56.227115 2018] [core:error] [pid 5224] [client 109.128.144.175:56373] End of script output before headers: index.php
[Thu Apr 12 21:09:01.321955 2018] [fcgid:warn] [pid 5225] (104)Connection reset by peer: [client 109.128.144.175:56374] mod_fcgid: error reading data from FastCGI server
[Thu Apr 12 21:09:01.322547 2018] [core:error] [pid 5225] [client 109.128.144.175:56374] End of script output before headers: setup.php

Any help would be very apprectiated.

Thnx.

Nobody any ideas? :s