Los Angeles-based Differential Brands Group, which has a portfolio of apparel lines, was this week’s biggest mover, gaining 33 percent to end at $6.40. West L.A.’s B. Riley Financial Inc. was also among the week’s movers. The financial advisory group gained 31 percent to end at $12.57. West L.A.-based Spark Networks Inc., which owns dating websites JDate and Christian Mingle, was the week’s biggest loser, dropping 12 percent to end at $1.74.