She may have developed an intolerance to something in that food. Try something different. At 6 years old my Lab started having a sour stomach and lots of gas, we switched him from his regular food to a lamb & rice food and he was fine.
she has been on the same food, kroger's old yellar, for 8 plus yrs now. no change in diet, treats nothing.
try a spoonful of honey given on a empty stomach...
this helps with stomach digestive problems ...
I would say the reason the dog has this problem is probably directly related to what you a feeding the dog ...what are you feeding him?
ne55