When Life turns your Lemons into Limes (and vice versa)

So I am notorious for ruining food. I just- cannot store certain foods for optimal shelf life. Take for instance, lemons. Limes. Flat leaf Italian Parsley. Oranges, bananas. Garlic, Onions, Shallots- you get the picture. So I am always reading up on how to store things properly. Somehow in spite of this I seem to have epic fails every time  I buy fresh produce. Take two weeks ago. I bought lemons, limes, potatoes, onions, shallots and garlic. And I was determined not to let anything spoil or go to waste. So, I put everything in my pantry (the bottom cupboard wedged between my fridge and my oven. The other day I went to grab a lemon and one of them had literally turned green. A powdery green film was covering one and a half lemons and spreading. I have had a lot of lemons grow bad on me but never quite like this. There was also some excess moisture in the grocery bag I left it in. So I pulled them all out of the cupboard and rinsed the green powder off the remaining lemons. Then today I pulled out my limes to go with the Carona that will accompany the wings that C is making tonight-- and my limes were turning yellow!

What did I do wrong guys? Was the cupboard a bad idea? Do you think the heat from the oven caused moisture in my tiny cupboard?

Please share your best food keeping secrets!
Thanks and have a great three day weekend!