I put some lettuce seeds into my poly tunnel and they were growing nicely, nearly time to pick em and they are going blotchy and yellow, is it a circulation problem I have been watering them of course. Just a bit worried for when I put Giant Toms and Runner beans in there. ???
You could have a read through this it may help
http://www.nr.gov.nl.ca/nr/agrifoods/crops/veg_pdfs/lettuce.pd