The spoiled foliage doesn't necessarily indicate a fungal infection of the roots, but it's a good indication SOMETHING is happening in the soil that is beyond the limits of what the plant is programmed to tolerate. top contenders would be over-watering, soil compaction and the lack of oxygen that comes with it, or a build-up of dissolved solids (salts) in the soil - which makes water uptake and movement to the plants most distal parts difficult. Since the most distal parts are leaf tips and margins, they usually bear the symptoms.
You/we can probably figure it out by answering these questions:
* When you water, do you water copiously enough that the entire soil mass is saturated and at least 20% (approximately) of the total volume of water used exits the drain hole?
* Do you allow water that collects in the collection saucer to be reabsorbed by the plant?
* Does your home have an ionic exchange water softening system (uses salt as the exchange medium)?
* How do you determine when it's time to water?
Al
