Explanation/Reference:
App3 was deployed using a service template. It should be updated using a service template.
To apply updates to a deployed service by using an updated service template In the VMs and Service workspace, select the service that you want to update with the updated service

template.
On the Service tab, in the Update group, click Set Template.

In the Change Service Template wizard, on the Updated Service Template page, select Replace the

current template with an updated template for this service.
Click Browse, select the updated service template, click OK, and then click Next.

On the Settings page, configure any application settings that are listed, and then click Next.

On the Update Method page, select whether you want to make the updates in-place to the existing

virtual machines or whether you want to deploy new virtual machines with the updated settings, and then click Next.
Reference: