Second seed Prerna Bhambri and Sharmada Balu, seeded fourth, also joined Shweta in the last-eight stage of the women's singles.
Mohit was leading 4-0 when his opponent Saurabh Patil conceded the match due to a lower-back problem, while Arjun Kadhe continued his impressive run with a 7-6(3), 6-3 win over Andhra boy Rishab Agarwal.
Vignesh notched up a 7-5, 6-3 win against Shaikh Abdullah, who is the top seed in the boys under-18. Nitten Kirrtane also made it to the quarter-finals of the men's singles with a 6-1, 6-0 verdict against Vilaser Khate.
In the women's singles, top seed Shweta knocked out Nehal Sahni 6-2, 6-2 and old warhorse Rushmi Chakravorthi got the better of Sahan Shetty 6-2, 6-4.
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The experience of Prerna was evident against Davanshi Bhimjiyani, who had the game and strokes to trouble the seasoned pro. The Maharashtra girl was not consistent and allowed Prerna to dictate terms even when she got the opportunity to get back into the match.
However, in the second set, Davanshi came out with more purpose and gave Prerna a tough fight. It was Davanmshi who took the initial lead in the second set, breaking Prerna in the second game but the Delhi girl returned the favour in the very next game. Divanshi did try to come back but all her efforts were thwarted by Prerna who did not let the match slip away from her.