Fluentd multiline log events missing fields - kubernetes

Question

I have log lines in Kubernetes:
2022-06-12T19:55:19.014511382Z stdout F dbug: Microsoft.Extensions.Http.DefaultHttpClientFactory[101]
2022-06-12T19:55:19.014515391Z stdout F Ending HttpMessageHandler cleanup cycle after 0.0016ms - processed: 0 items - remaining: 1 items
2022-06-12T19:55:29.010438412Z stdout F dbug: Microsoft.Extensions.Http.DefaultHttpClientFactory[100]
2022-06-12T19:55:29.010512909Z stdout F Starting HttpMessageHandler cleanup cycle with 1 items
2022-06-12T19:55:29.010518914Z stdout F dbug: Microsoft.Extensions.Http.DefaultHttpClientFactory[101]
2022-06-12T19:55:29.010532801Z stdout F Ending HttpMessageHandler cleanup cycle after 0.002ms - processed: 0 items - remaining: 1 items
I'm trying to parse these lines using the multiline plugin. I have the following config:
<source>
#type tail
#id in_tail_container_logs
path /var/log/containers/*namespace*.log
pos_file /var/log/fluentd-containers.log.pos
tag kubernetes.*
read_from_head true
<parse>
#type multiline
format_firstline /^(?<logtime>[^\]]*) \w+ \w (?<level>\w+): (?<classpath>(\w+\.?)+\[\d+\])/
format1 /^[^\]]* \w+ \w \s+ (?<message>.+)/
</parse>
</source>
<filter kubernetes.var.log.containers.**.log>
#type kubernetes_metadata
</filter>
<match kubernetes.var.log.containers.**namespace**.log>
#type loggly
loggly_url "https://logs-01.loggly.com/inputs/#{ENV['TOKEN']}/"
</match>
I can see the logs coming into Loggly, but they're missing all the fields I'm adding in the multiline parser's config. I have debug logging enabled and I can see that the loggly plugin is getting the records without the fields before sending them.
I tested the regular expressions against the lines individually using fluentular and they seem to work individually. Is there something I'm missing from my config that could be causing the fields to be missing?