I also had lettuce that looked like this (not my picture):
Should I pull out the entire root system? I harvested a few bucket fulls then it grew back covered in tiny white specks and brown spots along with the same damage under the leaves. Right now I have them cut all the way down...
My name is Inigo Montoya, you killed my father, prepare to read a tiny ad:
Devious Experiments for a Truly Passive Greenhouse!