I have found red mold of fungus on food from the fridge?

I have found red mold or fungus growing on food left in the fridge before(in a tupperware of leftover corn). I threw it away container and all before because of the color - bright magenta. But I made cupcakes three days ago. I popped them in the fridge to keep them fresh. I just got one out and took a few bites. There was a small spot of bright red inside. I looked to see if I might have been bleeding. nope. That stuff is growing on my food and this time I inadvertently ate it. Can anyone tell me what this might be? I don't understand how it could grow that fast in the fridge anyhow and its not like I think to tear apart my food to check it before I eat it. I feel sick but I am sure it is just psychological because I am disgusted that I ate something I wouldn't want to.