September 20 (SeeNews) - The blue-chip SOFIX index of the Bulgarian Stock Exchange (BSE) declined 0.49% to 553.69 points on Monday, hurt by a 6.11% decrease in the share price of battery manufacturer Monbat [BUL:MONB] and a 2.84% drop in the shares of diversified group Doverie United Holding [BUL:DUH].