When it comes to configuring agents through Kibana, you have two controls: service name and environment. As you stated they're all in your prod environment, you can only do this if they're different services (have a different service name).
To create service-specific configurations, visit the Agent Configuration page in the APM app, click "Create Configuration" and select the service name and environment you want to configure. Repeat to configure different sampling rates for different services/environments.
If you need greater control than this, then you can always configure the agents manually: https://www.elastic.co/guide/en/apm/agent/java/current/config-core.html#config-transaction-sample-rate