It's not needing VitC, it's needing to be fed. Do you ever target feed it? Still the water for 20 minutes, squeeze food from a turkey baster directly over it? I had a carpet anemone move behind some rock where I could not reach it and it went from dinner plate to 50 cent piece over a few months. Finally crawled back out about 2 months ago. Now that I can feed it again it has begun to grow.