A decade after making a killing during the financial crisis, Tricadia Capital Management has fallen on hard times. A slew of executives have left and assets have tumbled to about half of where they were at their peak. The credit hedge fund firm, started in 2003 by Arif Inayatullah and Michael Barnes, has suffered from withdrawals in recent years amid middling performance, according to people with knowledge of the matter. Blackstone Group LP, one of Tricadia’s biggest clients, has redeemed most of its investment, said two of the people, who asked not to be identified because the information is private.