skin splitting is usually linked to irregular watering. on very hot days they will have wanted more water than on cooler days. but if you have given the same amounts each day that will be why. as you say still perfectly edible.

Many thanks Seaburngirl for your reply

Yes, irregular watering! Often worse than yours though some split quite badly. I have watched out for this lately and for the first time, so splitting or scoring, so I did it right yay!