Two companies, SuperGroup and Keller, took a tumble on Thursday, both falling over 20% lower.Fast-growing fashion group SuperGroup failed to get its summer range out in time for the unseasonably warm weather seen recently, resulting in a lower sales growth rate in the three months to 1 May. Ground engineering specialist Keller warned that the impact of lower margins in the US, combined with the Australian floods and geopolitical issues in the Middle East and North Africa, mean it now expects group's EBIT for the year to be around 10% below that in 2010.Derivatives broker Tullett Prebon is under the weather after revenues fell 3% to £304m in the first four months of the year as the "world's financial markets remain unsettled." Industrial materials company, Cookson Group, said performance this year would be well ahead of 2010 and the firm was on track to hit targets set for 2013. Nevertheless, the stock is among the worst performers.The highest riser is specialist business publisher and trade events group Informa, which is on track for the full year, after first quarter revenues grew by 4.6%, helped by strong growth in Events and Training and a better-than-expected performance in Academic Information. Hikma Pharmaceuticals is wanted after saying it was on track to hit growth forecasts, with its operations businesses in Egypt, Tunisia and Bahrain performing well despite recent unrest. Meanwhile, miners Ferrexpo, Petropavlovsk and Kenmare Resources are in retreat on the back of falling commodity prices.---BCFTSE 250 - RisersInforma (INF) 441.20p +3.47%Rentokil Initial (RTO) 98.50p +3.41%Restaurant Group (RTN) 313.50p +3.36%Spirent Communications (SPT) 151.50p +3.27%National Express Group (NEX) 269.60p +2.51%Northumbrian Water Group (NWG) 365.20p +2.30%easyJet (EZJ) 365.10p +2.24%Misys (MSY) 360.00p +2.19%Stobart Group Ltd. (STOB) 137.00p +2.16%Hikma Pharmaceuticals (HIK) 823.00p +1.86%FTSE 250 - FallersSupergroup (SGP) 1,220.00p -22.49%Keller Group (KLR) 527.00p -20.27%Tullett Prebon (TLPR) 393.00p -5.87%Ferrexpo (FXPO) 452.50p -4.52%Petropavlovsk (POG) 814.50p -4.01%CPP Group (CPP) 123.50p -3.36%Gem Diamonds Ltd. (DI) (GEMD) 272.60p -3.33%Cookson Group (CKSN) 699.00p -3.19%Aquarius Platinum Ltd. (AQP) 332.40p -3.09%Kenmare Resources (KMR) 44.18p -3.01%