It's possible that the IP address range assigned by Internet provider B is flagged by bitnodes. io or other services due to previous activity or network behavior. This could result in your network being subject to additional scrutiny or review. If so, you need to contact Internet provider B's customer support.
This has to be the dumbest advice I've ever read. Do you really think ISP B's customer support even know what a Bitcoin node is, let alone know about bitnodes?
Most likely the customers of this ISP have their computers infected and being used for DDoS attacks. This is the only way I think could trigger a residential ISP's addresses to be reviewed for malicious activity.