So, I've used our MES about 8 times since we bought it last month. I'm noticing it looks pretty unsanitary in there (I'm used to clean pots and pans in the kitchen). The racks look great as well as the water pan and drip pan on the bottom but the rest of the inside is brown and has spatter and drip marks. Most of it doesn't just wipe off. Is this normal, or am I not caring for it properly?