Victoria Plum - deformed fruit

 This is my Victoria Plum tree, which is 3 years old and kept in container on patio (south facing garden).  I am getting fruit, around 30 showing at the minute but more than half seem to be deformed and breaking their skin.  I had similar problem last year and followed advise on feeding and watering but cannot seem to resolve this.

Can anyone tell me what is causing this and what I need to do - should I be removing all the deformed fruit?   many thanks.