I wouldn't turn them unless you take that one out first, keep it level, then turn, then put it back, assuming you are turning manually. It was maybe already started when they went in - no ideas how though unless they are from your own birds and Mum had sat for a day or so. Or - is it a duck - not a chicken? Eggs can look similar. I had one pipped early but it died when fully out as it still had a lot of yolk sac attached. HTH