Grayish "crust" on top of starter
I'm pretty new to sourdough but have maintained a successful starter for about a month now, and gotten some great breads out of it too. I've been feeding it 2x/day (roughly once every 12 hrs) with the ratio given in the handbook of 1/4 c starter, 1/4 c flour, & 2 Tbs water.
I got sick 2 weeks ago and fed it only 1x/day for several days. It still rises and falls normally, but about half of the starter turned a grayish-black. I've been trying to scrape some off and mix in the rest, but it will still separate once it rises.
I bumped the feedings back up to 2x/day, and the gray color turned much lighter, but it doesn't show any signs of going away. It's started to smell notably different as well--not bad, but sweeter.
Is the gray part alright to use for baking? Is there anything else I can do to get rid of it?