Daisy is a Rottie mix, right? I believe Rotties shed quite a bit, but yes - food definitely has an impact.
When I got my pit bull she was in poor condition, eating crap food and would shed so badly that if you touched her clouds of hair flew out.
She's been on Wellness for two years. Her coat is tight and glossy and shedding is so minimal as to be almost non-existant.
I'm not familiar with Performatrim.