Thanks to all. I have never added magnesium - I will try the epsom salt route. Also, recently I have changed to a mister that is fed by an RO filter but I still water the plants with well water that recently tested with a PH 6.3 - is that a problem?
Thanks - I thought that to begin with but after months of fertilizing it doesn't seem to be going away. Will these leaves never recover and I should just look to new growth to see if the situation has resolved?