Second m2 low performance

Hi everyone!

I have a question I've been wanting to answer for a while. I have a Gigabyte B650M-K motherboard, and I currently have an RX 6800 GPU. I have two M.2 slots with two M.2 drives (one PCIe 4 in the first slot and one PCIe 3.0 in the second), and I've noticed that with the second M.2 drive installed, my GPU's performance drops. If I disable it, my GPU's performance increases.

The manual doesn't say much, except that there are two PCIe x4 slots and the GPU's x16 slot.

Is this normal? I understand that some motherboards share lanes with the PCIe x16 slot and divide them with the M.2 drives, but I can't find much information about this motherboard. Could you help me? Thanks.