Can you see veins? A dead embryo sinks towards the narrow end of the egg and there will be a watery gap between the air cell and dead embryo with no veins visible in that gap. The dead embryo looks very black and will move as you move the egg.
I've also had a quail embryo stop growing but it lived for about a week before finally dying (I candled daily). So that was pretty sad.
By 19 days they should all be full and almost ready to go.
I have the same issue with one of my eggs in lockdown right now but the thing still has veins and is moving so . Also there is no real hard or fast rule to humidity % really I heard from 60% up to 75% but it depends on lots of factors. Good luck
Ok it started yesterday at about lunch I noticed a pip. Then she/started unzipping but has now stopped... nothing all night. But the little tooth is moving around and she’s trying desperately to break it... what do I do.