Stackstorm Blueprint box memory usage is high

I have three blueprint boxes in a HA environment. On it, there are only two sensors and a workflow. Still, each of them uses a lot of RAM.

840.066MB 21458 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2garbagecollector --config-file /etc/st2/st2.conf
845.285MB 21468 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2sensorcontainer --config-file /etc/st2/st2.conf
853.816MB 21473 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2timersengine --config-file /etc/st2/st2.conf
863.25MB 21461 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2notifier --config-file /etc/st2/st2.conf
864.566MB 21431 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
864.742MB 21423 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
864.754MB 21415 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
865.145MB 21417 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
865.266MB 21427 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
865.418MB 21434 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
865.578MB 21419 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
866.035MB 21476 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2workflowengine --config-file /etc/st2/st2.conf
866.531MB 21421 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
867.25MB 21429 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
867.492MB 21425 root /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2actionrunner --config-file /etc/st2/st2.conf
888.445MB 21465 st2 /opt/stackstorm/st2/bin/python /opt/stackstorm/st2/bin/st2rulesengine --config-file /etc/st2/st2.conf

ps -eo rss,pid,euser,args:100 --sort %mem | grep -v mistral | grep -i '/opt/stackstorm' | awk '{sum+=$1} END {print sum / 1024}'
15380.1

Stackstorm is using almost 15GB RAM in all the boxes. How can it be resolved?

Start by reviewing the listed st2garbagecollector, st2sensorcontainer, st2timersengine, st2notifier, st2actionrunner, st2workflowengine, and st2rulesengine processes along with /etc/stackstorm/st2.conf. Reproduce the memory measurements in the reported HA setup and determine whether the high usage is expected or grows over time; done means identifying the cause and documenting a verified resolution.