Vitiligo in 4 years baby. In young age.

First there was a single grey hair one year back..then I gave biotin multivitamins..she was ok .. then there pale white spots on her face as every child gets.. we consulted dermatologist doctor gave dewmoist lotion and peacon cream...spots were covering up.. then suddenly I saw white patch on her scalp..we thought it may b fungal infection..but when we went to doctor ,doctor saw patch n one or 2 hairs on that patch were white..doctor said it's vitiligo.. we are so much worried now.. doctor prescribed her vitibex tab ,zincovit syrup,then flutivate e cream on patch and sun exposure for 10min in morning n afternoon.. we are really really worried n scared in such small age she is facing all this.. hoping treatment will work for her.. we don't want it to spread at all.. why all this happens in young age ..please give suggestions and strength..