Publishing a processed input to multiple mqtt brokers

I have a version 11.4.5 low write of emoncms running on a Raspberry Pi. In general it runs very well reading 7 DS18S20 sensors.

I am now integrating it into my home system via my home mqtt broker and have multiple mqtt configurations set up in the emonhub.conf file (MQTT, MQTT1 and MQTT2). This works OK and the temperature INPUTS are published to all the brokers when the readings are made.

The following shows the initial broker connections being successfully made:
brave_foeiF9Wg7K

And this shows the various inputs being published across the 3 brokers:.

I calculate temperature differences in an input stream and also want to publish these (and other calculated feeds). Even though I log these to a feed and add “Publish to MQTT” the messages are never sent - except to the local broker.

This is the onboard broker (127.0.0.1) showing the calculated messages (eg Solar_deltaT)
MQTT_Explorer_dUs9KFE5Fb

This is another broker. The Solar topic messages are not received.
MQTT_Explorer_8RkYauW5Wt

I can’t figure out what I am doing wrong. I had assumed that when you use the Publish to MQTT process on an input then it would send to all the configured MQTT brokers. Is this not the case?

Any help would be appreciated.

I have looked at Community topic Publish Feed value to MQTT but this doesn’t seem to go as far as I am trying to do with multiple brokers.

Cheers.