Hi Willeke!
I'm glad you posted this question. It made me peruse the internet to find answers to this issue and I learned a number of things. 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). And this browning of leaf tips occurs in virtually any plant form.
@RickCorey What say you?
