Viewing post #1071576 by Rainbow

Rainbow said:The reason runs the gamut: over-watering, under-watering, too much fertilizer, salt build-up, fluoride in the water, climate change, transplanting...and many other reasons that cause stress to the plant.

Bottom line is that it is not caused by a disease...it is a symptom of the plant having gone through some kind of stress (past tense).

Willeke, the new leaves are not affected, so perhaps the cause had been rectified already. Flushing every other week is a good idea.