It wasn't quite clear to me if you are trying to mine with all 3 cards at the same time but here is what I have to say.

You CANNOT mine with both AMD and NVIDIA cards at the same time, using the same miner. The 2 different card companies use different drivers that the mining software utilises.

You CAN however still mine all 3 cards at the same time, but you need to use different instances for different brands of GPU's. For example, Claymores latest Ethereum miner is designed for both AMD and Nvidia cards, but you need to load 1 instance for the AMD cards (and specify which PCI slots the AMD cards are using) and another instance for the NVIDIA cards (and specify which PCI slots they use).