It’s always been the case that you should only have one Auth token per device, and this has been true right from when I started using Blynk more than 6 years ago.
Blynk have clearly decided to implement a system that prevents people from “cheating the system” by sharing Auth tokens across multiple devices.
I don’t think it needs them to pre-announce that the system now enforces what should always have been a rule, but that’s just my opinion.
You’ve not explained much about how you’re using Node-Red. My whole home automation system is based around Node-Red and Blynk, but I don’t run any Blynk code, or have any Blynk Auth tokens on any of my ESP devices. I use the Blynk IoT contrib for Blynk so the only thing that Blynk is a single Node-Red connection that uses a single Auth token.
Node-Red talks to my ESP devices via MQTT, and Blynk is totally unaware of these devices. I have around 25 devices connected to Node-Red, most of which either feed data to MQTT then on to Blynk, or which can be controlled from Blynk. But, as far as Blynk is concerned I have just one device, which is my single Node-Red connection.
The limiting factor is usually the number of datastreams available to communicate with Blynk, and the number of widgets available - all of which are limited by your subscription.
More info on my setup here…
Pete.