The anal sacs normally empty and refill every day. When stools aren't firm enough, however, they don't exert enough pressure to empty the sacs. This causes fluid to accumulate, making the anal area itchy and sore.
It is considered that diet is the main cause of the anal glands not emptying naturally and problems occurring. Eukanuba does not provide a balanced diet.
Like Odin-Genie suggested I would try Artemis dog food.
Just remember that changing the main ingredient of your dog's diet (e.g.: brand of dry dog food) should be done gradually and over a period of at least four days (preferably longer).
Example:
On the first day of change, you should have plenty of the old dog food left. Add three quarters of their old food, and one quarter of the new food. You should do this for at least two days. After two days or so, add in another quarter, so you have half old food, half new food. Again, keep it at this level for another two days or so. Then add in a third quarter (one quarter old, three quarters new), and finally you can phase out the old food completely.
This worked for our 14 month old Lab x =) No anal glands problems here.