Posted: 07/06/2014 at 13:41
Are they in the ground or in pots? I only ask because in pots they might be congested if you have a lot of them, and therefore they could be short of food and water, and in the ground it could be slug/snail damage. Regular picking usually means more flowers, not less.
DavidK is the SP expert but I don't know if he's around today.