My Sourdough Starter has a brown layer at the top? So my sourdough starter is about two weeks old, but it suddenly stopped growing three days ago (after a couple days of very active growth)and developed a brown layer on top.The layer is mostly brown with about 15 percent of it being normal starter. Most of what I researched is that it is hooch, but the brown layer is more solid (the same thickness as my starter) and isn’t separate from the top layer of the normal starter. I have been keeping my starter in the oven with just the light on. As for my feeding schedule, I feed it 1 cup of AP Flour and 1/2 cup of water every day. If anyone has an answer, please let me know; it would very helpful.
Your starter is drying out. Don't keep it in the oven with the light on. It's been too warm. 

Depending on your comfortable room temperature, you should be able to leave it on a kitchen counter top. You should have a lid or other covering on it, too.