propane slow leak question

i already soaped the stove supply line, in fact i have soaped about everyhting, have not crawled underneath though. i have replaced both pigtails. you are right, it is not a large amount of gas,,,,but!!! i don't think it was doing it before cause i generally leave my one tank on and it has never run dry. after it hit 6 inches, it only took about another 2 hours and it was completely at "0" pressure. i would say from about 7.2 inches of pressure to empty took about 3-4 hours.

my one question, does anyone have the experience to say whether or not this amount of a leak should show bubbles?