Answer: Your ficus tree may be responding to dry air, too much or too little water, too much fertilizer, or water high in salts.
Ficus likes moist soil (but not soggy wet soil), bright light with protection from hot afternoon sun, and some humidity in the air. If the air is overly dry, which sometimes happens when we have the heaters running in the winter, plant health can be compromised. Adjust this by misting your ficus every few days.
If your water is high in salts, try using bottled water for your plants.
Fertilizer burn shows up on plant leaves in the manner you describe. If you fertilized your ficus, it may have gotten too much. You can counteract this by leaching the soil. Flood the container with water until it flows out of the drainage holes. Wait 30 minutes and flood again. Wait another 30 minutes and flood a third time. Then allow to drain. This repeated flooding should leach out excess salts.
Hope your ficus regains its health!
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