Erich,
Zebras require lots of bright, indirect light - a few hours of direct sunlight each day is better. They are fussy about watering, preferring constantly moist (not soggy) soil. Water thoroughly as soon as the soil surface dries. Even an occasional lapse in watering can cause leaf drop.
Fertilizers are food, not medicine, and are not beneficial to ailing
plants which don't uptake many nutrients.
You might find this
thread helpful. Feel free to ask if you still have questions. I doubt using city water the cause of the Zebra's problems. Most
plant problems arise from improper light, watering practices, or overpotting. Did you recently repot the Zebra?
Cricket