With all 3 pictures that you sent, I see that our 3090 is not using its full potential because it’s only using 269w when it should use around 340w.
Few things come to my mind.
1°) Do you have enough wattage from your PSU to run all your cards?
2°) Did you check that all cable going from the PSU to the GPU and from the GPU to the risers are well connected?
3°) Did you try to swap your risers?
4°) Did you update to the LATEST NVIDIA DRIVER? (I see that you are using the version 455.45.01 and I am using the version 460.67.
Your problem might be coming from that.
To do update your Nvidia drivers, check this out: https://hiveos.farm/guides-driver_upd/
Tldr: Command shell and type: nvidia-driver-update --list
Select the latest stable driver by typing the version and reboot your rig.
5°) Try switching your mining software, I am using T-Rex Miner and I have no problem, try others, that may fix your problem.
6°) Try downgrading your HiveOS version, I had the latest HiveOS but it didn’t detect the RX 6700XT so I had to downgrade it. (not too convince about that one but you got to explore all posibilities)
7°) Open your GPU and check that everything looks normal inside (you can switch some thermal pads while you are at it
8°) Your GPU might be throttling and that’s why you are getting low hashrate, it’s simply too hot for the Memory to handle.
The 3090 are really really hot, so try to give your GPU as much airflow as you can.
If you can boil an egg on the backplate, it’s too hot.
I can’t let my hand my 3090 more than 1 sec and the core is at 50°C, so when I see yours at 61°C I imagine that your GPU MEMORY might be very very hot.
I put my AC right in front of my rig so that’s why it’s not that bad.