It seems like the issue you're experiencing with the meshes appearing as rectangles in Unity could be related to the export and import settings of your Spine project. Here are a few steps and checks you can perform to resolve this issue:

1. Check Spine Export Settings:

   • Ensure that your export settings in Spine are correct. Specifically, check the settings for the texture packer and make sure you are not stripping whitespace or using settings that might affect the mesh shapes.

2. Check Unity Import Settings:

   • Verify that the import settings in Unity match the export settings from Spine. This includes checking the texture import settings and ensuring that the material settings are correctly configured.

3. Premultiplied Alpha vs Straight Alpha:

   • Make sure that the alpha settings match between Spine and Unity. If you exported with premultiplied alpha, ensure that Unity is set to handle premultiplied alpha as well. Refer to the documentation on [Premultiplied vs Straight Alpha Import](http://esotericsoftware.com/spine-unity#Advanced