Service Replicas are not spread for Mutli Service Stack

Hi community,
I have deployed a stack with a of 4 services on two hosts (docker compose version 3).
The services are Elasticsearch, Kibana. Redis, Visualiser and finally my Web App. I have’t set any resource restrictions yet.
I spun two virtual host via docker-machine , one with 2GB and one with 1GB.
Then I increased the replicas of my web app to 2 replicas, which resolved to the following distribution:

Host1 (Master):
Kibana, Redis, Web App, Visualiser, WebApp

Host2 (Worker):

Why is the Swarm Manager distributing both Web App Containers to the same host. Wouldn’t it be smarter if Web App is distributed to both hosts?
Besides node tagging I couldn’t find any other way in the docs to influence the distribution.
Do I miss something?