Tim you might be right, I was thinking that the newspaper is more permeable than plastic and perhaps too much moisture is being evaporated through the walls of the pots. I have been needing to water them more often than the others as they dry out a lot quicker. But I have been keeping them moist but not waterlogged. They just look very stunted, and this has happened with melon, squash/pumpkin, peppers, tomatoes and chilli. Only thing that seemed to grow really well in them was the sweetpeas.