This might not be the best place for your mining question.
I would go to Mining Websites Forums that uses your mining software to get better answers. Most likely, a miner like yourself, will be able to guide you on how to set up your PC so that it will work with all the GPUs you have installed or help you troubleshoot your issue.
But maybe someone with mining experience here can help you out.
Which Mining software and version are your using?
How are all of your GPUs connected to the motherboard? Using Risers or directly on the Motherboard?
Which AMD Driver are you using and version?
Some Users here are a little sensitive to Miners since they are one of the major reasons there is such a large shortage of GPUs in the market.