I bought calabrese plants and planted them in my polytunnel , about 4 weeks ago. They have grown well but the leaves are loosing colour, becoming spotted and slightly pale or yellowish looking. Is this normal, are they thriving or dying?
It is not normal that the leaves are spotted or yellowish. In a tunnel, this might be caused by intermittent drought. Outdoors it could be caused by cabbage root fly, which is unusual in a tunnel, but not impossible, especially if the doors are open quite a lot to admit the flies. If the plants wilt, it is a sign of cabbage root flies and the grubs can be seen on the roots.