Mid-cap stocks were up slightly on Thursday, by 1.07% at 16:42, with power generator Drax leading the upward charge.The power company put in a solid performance after tumbling to an all-time low on Wednesday after Chancellor of the Exchequer George Osborne announced the government will remove the Climate Change Levy exemption for renewable electricity generated after 1 August 2015.Drax said it expects the change to lead to a reduction in earnings before interest, tax, depreciation and amortisation of around £30m in 2015 and £60m in 2016.The second fastest climber SuperGroup rose 7.17% to 1,330p after posting a 2% rise in pre-tax proit. The clothing retailer also said it signed a joint venture that will allow it to enter the Chinese market.Recruitment firm Hays also had a strong performance as it said second half operating profits would come in ahead of those seen in the first half of the year.Hays shares were up despite the company warning foreign exchange movements would continue to impact profitability.Shares in DIY firm Grafton Group took the biggest dip of the mid-caps after the company said in an update margins were modest.The company said revenue for the six months to June 30 increased by 6.6% from to £1.015bn to £1.08 bn, despite weaker pricing in the UK plumbing and heating market and a competitive market.Debenhams shares fell after UBS downgraded the stock to 'neutral' from 'buy', saying the risk-reward ratio was now balanced.UBS said Debenhams was almost halfway through the gross margin focused strategy and there has been a net gross margin benefit of only 10-20 basis points.Stock in Fidelity China Special Situations and Man Group bounced back, tracking overnight gains in Shanghai shares.