Even though it says that the pool closed connection remotely, I guess it could still be due to networking problems on your side? Can you check your network, whether the adapter in the rig works ok, the cable is alright and the router is functioning correctly?

This is also a valid question to the pool support. Run the miners with logging enabled and then contact the pool and send them relevant parts from those logs, asking why this could be happening. Maybe there's something in your miner's configuration that the pools don't like.