Just to update, the coturnix hence hatched her chicks yesterday. It was later than expected as I was counting from egg seven as she started sitting then but calculations work out at 15 days from the last egg laid. I don't know how they time it? The sitting prior to the last egg must be just keeping the eggs from going bad maybe?
Anyways she had 8 chicks hatch from the 11 eggs. One chick got squashed somehow and was dead. Or maybe it died for another reason and then got squashed? Anyways... I removed it and empty shells whilst my female was getting a drink.
The remaining three eggs I've left to see if they are late hatchers (could be last eggs laid are slower development) or maybe they are first eggs laid and are duds due to waiting longer before she sat on them?
The day before they hatched I gave the whole area a full clean out which the female didn't like at all and she flew out the pen. But she still went back to her nest after it was all done so she didn't give up on her nest despite disturbances over the course of incubating!