Just doing a quick search on sluggish/blue tipped comb/ egg laying slowing down or stopping... sounds like there may be a heart problem. Chickens sometimes do have heart problems and when the heart gives out it's fast. Happens very quickly and there is really nothing that can be done if that is the case except for waiting and giving her what she needs. Other blue tipped issues were frost bite but this time of year that would not be the problem. I hope someone else will have some ideas too here soon but that's what I found so far. I will keep looking for you.
