fsadough might be the best person to answer your question.
Also need to give all the specific information that he will probably need like Current Windows version installed, How are all 6 monitors connected to the GPU, Current AMD Driver installed, basically your computer setup.
With the information you provided, no one will be able to assist you. It is like going to a physician and say I am not feeling well. You need to provide detailed information, like:
1. 5x LG 98LS95D
1x samsung 32 CHG70
2. all LG screens are connected with a mini DP to HDMI adaptor wich goes to an active HDMI to SDI converter.
The samsung screen is connected with a mini DP to DP cable.
EDID is forced on the LG displays.
3. I'm using win10 and all the latest drivers are installed (graphics card and screens)
4. All screens are set to 50Hz
The problem is that I cannot set the samsung display resolution higher than 1920x1080, even it supports 2560x1600.
Hope this information helps.