I have 2 different blueberries ( as recommended) planted in large pots. the last 2 years they have fruited quite well. they are in ericacious compost and I fed them during the spring to get them going again after the winter. I pruned out the centre stems to create a bowl shape to let more air into the plants. But only about 6 berries between them this year. should I have pruned them harder, if so when? What should I do to get more fruit next year?