Oakley, I was just reading that humidity is a factor as well, for 'edema' or 'intumescence'. There are a number of contributing causes, one of them is that UV-B is involved in stomatal function, at least for some cultivars it can cause a failure to open and transpire when needed, resulting in what is basically a water injury to the plant. High humidity evidently causes this as well.
Here's a link that offers a list of preventive measures:
https://ag.umass.edu/greenhouse-flor...a-intumescence