Splitting normally happens due to overwatering. Could this be the problem?

The cause of fruit split of this nature is erratic temperatures and/or irregular water supplies - if they go a bit dry when the fruit is swelling, and then get well watered, the fruits start to swell rapidly, absorbing the water, and the skin can't keep up, so it splits. They do need copious amounts of water on a regular basis to try and prevent this... but extremes of temperature, to some extent, are more easily controllable when the plants are in pots and able to to be moved. More info via the link below

https://www.rhs.org.uk/advice/profile?pid=393