Add-On Overriding Theme's Style Sheet

Hello,

I’ve come across a problem with the Download Manager Plugin, as well as the Button Add-Ons. I’m currently using the Kedavra Theme from Theme Awesome. They have these transparent buttons that display text and a border. But after a day or two of running Download Manager and the Add-Ons, those buttons became a big white block.

I emailed my theme provider and they said that WP Download Manager and the Add-Ons are causing this problem and I need to remove them. Sadly, after I removed them my website buttons looked perfect again. So my question, is there anyway to set up WP Download Manager and the Add-Ons to work together with my theme and not override the existing styles?

Thank you!