Double gold and exp?

Today i was in HM running the hydra farm and i was still getting only 300 exp and 100 or so gold drops witch is what ive always gotten. Why am i not getting more gold and exp?

The double only applies when you vanquish the entire area, meaning you kill every single creature.

For info on vanquishing: http://wiki.guildwars.com/wiki/Legendary_Vanquisher

"When an area has been successfully vanquished, a message will appear to notify you of your success. You will then be rewarded with both experience and gold equal to five times the number of monsters defeated in the area."