I had a similar problem in my greenhouse. Healthy plants moved from house to greenhouse, after initial good growth, leaves wilted and plants became unviable. This happened again the next year so I abandoned the greenhouse for tomatoes. Some time after I moved the greenhouse to another site, inc; dismantling, thoroughly cleaning glass and frame with Jeyes Fluid and re-erecting. I have had no problems for 2 years now. I think it was a disease possibly harboured by insects or spores in the structure.
Pete