The aim should always be to keep the soil moisture as constant as possible whether growing inside or out, in soil or compost - blossom end rot is mostly caused by inconsistent watering, as well as the problems mum has already mentioned.
Whatever your watering regime, try not to wet the leaves when doing so - obviously natural rainfall does exactly that, but it makes sense to do what you can to minimise the chances of blight taking hold at this time of year.