I'm having a really strange issue with the rich text editor in a canvas app. I have several multiple line of text fields, all enhanced rich text in a SharePoint list. In the Canvas app, I removed the default text box, replaced with rich text editors, updated all the properties and it works perfectly in the development environment.
Once I publish the app, the rich text editors are TINY. Their width property was set to Parent.Width - 60 which is the default width for all fields in a default card.
Here is the development environment:

And here is the published Canvas app:

I've done this with custom SharePoint list forms with no problems at all. This is the first time I've used the RTE in a Canvas App.
Because the app is not going to be used on a mobile device but on laptops, I had to reduce the default font size in all fields from 21/24 to 10.5.
Does anyone have any ideas why this is happening and how to resolve it?
Thanks!