I have a batch of King Arthur sourdough starter that I mixed up several months ago and have been using ever since. I keep it in the refrigerator and feed it with 100 g of AP flour and 100 g of water once a week. I have made several hybrid loaves with it with no issues. I have noticed that at the end of the week when I am ready to feed it, it seems to have an orange-pink coating that has a strong citrus smell. I assume that it is some kind of fungus. I live in north Florida. It does not seem to be harmful in any way; I've made several loaves since I noticed it and have never gotten sick.
Any idea what it might be?
UPDATE Here is a picture of the starter. In the lower left, you can see an orange tint.