Bain Capital and Blackstone Inc. are among private equity firms in the next round of bidding for Vitabiotics Ltd., the UK vitamin company led by ex-Dragons’ Den investor Tej Lalvani, according to people familiar with the matter. EQT AB and TPG Inc. have also proceeded in the bidding process for Vitabiotics, which sells some of the UK’s most popular supplement brands, the people said. Representatives for Bain, Blackstone, EQT, TPG and Vitabiotics declined to comment. Vitabiotics sells vitamins under brands including Wellman, Wellwoman, Pregnacare and Wellbaby. Between class-action lawsuits, safety fears and customer dissatisfaction, the vitamin, supplements and minerals industry is facing more scrutiny than ever.