Plex only at lower resolutions

I just bought a TiVo bolt and activated the Plex app. Whenever I try to watch the movies from my server they will only show on the bolt if I lower the resolution to 720 P and two megs the second speed. I am able to use all three other streaming boxes that I have to watch the movies at their normal 1080 P resolution. These boxes include a Roku three, and AppleTV 4, and a fire TV.