It may due to the cache on your site, cache may loading the previous CSS. So, kindly check the site on other devices or clear the cache and check again.
We checked all steps for updating from 1.2.1 to 1.3.0 and it’s working fine here. You may just get a extra section on the Home Page, and you can easily hide that section from Appearance > Customize > Layout/Design Options > Front Page content option and all the remaining things are working fine. Would you please provide the link of your site so that we can check everything on your site as well. And thank you so much for using support forum for the issues. We will be happy to solve your every issues related on our products.
Waiting for your reply.