Had my Edge to the dealer 2x. Drove it for 6 months no problem. Then all of a sudden the message to check brake fluid was on. Filled it up drove it a week it was down again. Took it to the dealer they could find no leak. Brought it home. 2wks later checked fluid it was down a good inch. Work at home so it only has 3500 miles on it since May and was bought with 160 on it. brought it back and they still can not find a leak. Any ideas?