Eukanuba Senior Lamb 1st Ingredient Dry Dog Food, 30-lb bag

I have a 12 yr old black mouth cur. I have been through 3 different brands of food in the past 4 months. I purchased this after diligent research and very highly rated reviews and 3rd party recommendations. Unfortunately, I overlooked a specific ingredient placed rather high in the ingredients list. That ingredient is sodium hexametaphosphate. Go ahead and look it up. I'll wait. He really liked the food for the first week or two, but became extremely lethargic in the morning every other day. To the point where he was walking slow and wanted back inside shortly after being let out. Which is very unusual. For the past week and a half I have been taking off of work. That's how worried I have been. Now, after taking a critical eye to the ingredients list (I admit, with his problems with other food recently I sort of purchased this impulsively) I'm blaming the food. Back to the drawing board. AGAIN. I omitted giving one star because there are pros to this food. It is much softer than most other dry food I have purchased, which is a big plus for senior dogs with dental issues. And the bag arrived airtight, with a quality ziplock seal not found with other brands. He has gotten sick less with this food (aside from expelling a bit of foam once every two weeks or so), but his energy is WAY off, hiding in the front room a lot, he's licking his hind legs quite a bit, and something just seems terribly wrong. Along with that, his poops have been very thin as well lately. Just noting this in case anyone else starts noticing issues with their pups and can deduct that the food may very well be a common link. I really wanted this food to work out. But it seemsjust another brand using questionable ingredients to me.