Third seed Arvindh Chithabaram continued his winning run to maintain lead along with compatriots and sixth seed B Kumaran and 17th seed Al Muthaiah with four points apiece.
Second seed Murali Karthikeyan bounced back with a win over Mitrabha Guha of Bengal to be on the second position along with eight seed Pranav Vijay, Neelash Saha and four others with 3.5 points each.
Diptayan was caught off-guard when Krishna Teja took Nimzo Indian variation with tactical mid game.
It was Arvindh who showed immense maturity to overcome a strong challenge from Bharathakoti of Andhra Pradesh.
In the girls section, top seed M Mahalakshmi and third seed R Vaishali maintained lead with all win records after fourth round.