MUMBAI : Edtech unicorn Byju’s suffered a twin blow with its statutory auditor and three external board members stepping down, adding to troubles for the company battling lenders, lawsuits, and a funding winter. Deloitte’s resignation note cited five letters it wrote to founder and managing director Byju Raveendran and board members on 30 September, 5 November, 12 November, and 24 …