Tell harmless mineral spots from disease with a simple wipe test and change of watering technique.
Wipe test
Dampen a microfiber cloth. If the white haze lifts cleanly and does not return after a few days (with no splashing), it was mineral residue, not mildew.
Source & prevention
Hard water leaves calcium deposits when droplets dry on leaf surfaces. Water at soil level, use a long-spout can, and avoid misting sensitive foliage.
Gentle cleaning
Use distilled water or a tiny splash of vinegar in water (spot test first). Wipe in one direction to avoid scratching the cuticle.
