Sorry folks I'm going to blather on about water again. Got to thinking about this at 3.00am!!
@Tenkaykev I now think you're very likely bob on with the creosote theory. Everything on my allotment from emerging seedlings through to tomatoes in containers for 7-8 months is watered from stored rainwater. If we run out I collect water from a nearby spring. It's very rare for me to lose plants through watering.
I store +/- 900 litres of which 90% is run off from my shed roof. The roof is covered with mineral felt held down with zinc nails and batons at the edges. Your felt is stuck down with creosote so I agree you probably have low level contamination which you're misting directly on to the foliage. Fascinating, sorry!
I've only ever seen creosote damage on plants too close to recently painted fences.
One other remark and I promise to go away and start my own thread on plants and water. You might feel my view on when to water conflicts with what you read. It probably does.
Commercial growers, especially bedding growers, use water in two ways - to stimulate growth and control growth. Therefore decisions about watering are taken based on how the crop looks, what do we want it to do, do we want to accelerate growth, slow growth etc. The amount of water actually in the compost isn't the first consideration.
Good growers can control plant growth simply through water use. This eliminates the need to chuck a lot of growth regulator chemicals on the crop.
I'm off out.
, council tax £3 cheaper per month 
