If they are selling 7% less, that's a BIG loss of sales, and a big problem to turn around (future discounting so lower profits)
Take a look at what happened to GNE a year back when they reported a decline in customers. The SP was hammered.
Today also seems to be a "down day" for the generators across the board, so probably some effect from general market sentiment to this group of stocks as well
I personally don't rate MRP highly in the electricity generator/retailer category, but everyone has a different view on each companies merits