Help with tomatoes problem needed

Can anybody help, I've just returned from a couple of days away and all my cherry toms plants which were growing fine have now started to develop a problem. All the lower leaves have started to curl up and are covered with browny gray markings especially along the veins of the leaves. Anybody got any idea of what is going on and is there anything I can do to cure it.
Any suggestions greatly appreciated

 

Hello awizzbang,are the leaves brown on the underside and yellow on the surface?If yes it could be leaf mould.Spray with carbendazim and remove some of the lower leaves.Ventilate the gh especially at night.