I just bought a cast iron pan from Lodge. It says it's pre-seasoned. Problem number one, Everything sticks to it and number two, anything light-colored I cook in it comes out black. I tried making Swiss Rosti in it and I had to scrape it off the bottom of the pan and the potatoes turned black. I also cooked asparagus in olive oil w/ garlic and the garlic and oil turned out black also. Any suggestions?