Nitya won the gold while compatriot Ankita Shah won the silver in kata technique in the girls under 7 years category.
Mehta added the individual kata gold to the team gold he won yesterday in the boys under 13 years group to complete a double crown.
The corresponding individual gold in the under 8 boys category was clinched by Dave who edged out South Africa's Daman Botha.
In the kata for girls below 9 years category, India's Stuti Bhattacharya won the bronze while South Africa's Kyra King won the gold medal with Iran's Jefarzadah Aylin pocketing the silver.
India's Kaninhka Kareekar won the kata bronze in girls below 11 years category behind South Africans Lyucay Weidman and Shanay Archery, in that order.
In the kata contest for boys below nine years, India's Zayed Shirji and Prajwal Patil won bronze medals with Thailand's Tomoki Miki winning the gold and South Africa's Jordyn Pretorivs grabbing the silver.