The hair cycle normally consists of growing, resting and falling hairs and there is a delicate balance between these stages of hair cycle. Normally hair should re-grow but if it is not happening, you should consider seeing a dermatologist. It should be okay, just that mehandi can cause dryness and you may have to use a conditioner
Further information is in the following weblink
https://www.aad.org/public/diseases/hair-and-scalp-problems/hair-loss
Next Steps
You can meet a qualified Dermatologist with MD/DNB/DDVL/DVD degree for proper examination.
Health Tips
You can consult me online for personal recommendations.