[Observium] Memory stats not showing on Juniper MX204s

Hi all,

We've just swapped out some Juniper MX80's for MX204s:

https://www.juniper.net/us/en/products-services/routing/mx-series/mx204/

and we are running Juniper JunOS 18.2R1.9 ([MX204] Internet Router). We didn't add a new device, but Observium picked it up OK as it has the same details.

But I've now noticed memory usage has gone. Any tips?