Mold growth on cheese not working

I am concerned about my Biology 2 lab experiment we are supposed to grow something and be able to measure it for 10 days. My experiment is seeing how pH affects mold growth on Land O Lakes Yellow American cheese. I am using lemon juice for the acid baking soda diluted with water for the base, sugar water for the neutral, and tap water for the control. The cheese are placed in zip lock bags open, and in a room with the temperature range from 65 to 68. My problem is that it has been over a month and no mold has grown on any of the cheeses and I don’t know what I am doing wrong