Pepper Sweet Sunshine

Has anyone grown Sweet Pepper F1 Sweet Sunshine? I am growing 10 different varieties of sweet peppers and chillies. 9 of the varieties look great, all have plenty of fruit and flowers. I have 4 pots of Sweet Sunshine which to be honest look pretty pathetic. They are about 3 inches high and seem reluctant to put on any top growth. I am not impressed with their root growth either. One of them has a couple of very tiny flowers. I have not treated them any differently from the other varieties so I wonder if anyone knows if they need any special treatment? At the moment I would not bother growing them again. Thanks. ( They are in a greenhouse by the way, in 1 litre pots as the packet recommended-although I now wonder why I potted them on! I have shown them the compost bin as well!)