I had a look at the ingredients and I understand your concern. Not a food I would want to feed my dog. Personally I feed NRG dehydrated, but it is expensive and you are feeding three. You might get better mileage out of your food if you fed your dogs separately. I assume the overweight male may be getting more than his fair share?
BTW, how tall is your 28 pound female? That seems pretty heavy for a boy, let alone a girl in "perfect shape"! The 23 pound girls sounds to me to be normal weight.
We feed Ancana here and have had good results with that. My guys get the Grasslands formula, but there are also a couple of others with different protein sources. One of them is fish based.
They also recently have brought out limited ingredient formulas for dogs that have allergies. All the formulas they make are grain free.
There are several other good dry foods out there. Orijen, Earthborn, Instinct, and Canine Caviar just to name a few examples 
When shopping for a good brand check the ingredients, the meat sources should always be listed among the first five ingredients.
Besides getting a better quality food than SD, I would highly suggest you don't feed them all together. You don't know how much each gets by feeding them all together, consider feeding separate so that you can measure out the food and you know who is eating what….
I feed Natural Balance Sweet Potato and Fish. Seems to agree with everyone. Norah was allergic to Chicken Soup for the Dog Lovers Soul.
There are a lot of good, high quality foods so buy small bags to let them sample till you find one they all like, and it 'likes them' (stools not loose). I fed Innova for years, then EVO, then Orijen, but the last 2 were too rich for mine. I used to feel all together but last year started feeding them measured food in separate bowls. Ed & NIcky are a nice weight, but Chipley is a moose, even with thyroid meds and eating measured low fat/calorie foods.
I am currently feeding a Natural Balance food and it agrees with everyone. There is no one perfect food, just read ingredients and go for quality!
Since your one dog has intestinal problems, you should definitely look at the ingredients on the bag. All my Bs get different food and are fed separately in their crates. One has intestinal problems, one has allergies, and one gains weight easily even though she is on thryoid medication, and if you do not feed her enough, she will chew and eat anything.
Jennifer
We do all kinds of food. For kibble brands, we use and have liked Taste of the Wild (despite recent recall problems), Canidae, Acana, Fromm's, Pinnacle, Great Life, Timberwolf Organics. I'm sort of obsessive about tracking just who ate what, so I agree that separate feeding is the way to go.
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Personally I feed NRG dehydrated, but it is expensive…
NRG dehydrated is a regular at our house - Kipawa LOVES it. We do a half and half of NRG and Acana kibble and then add some additional raw vegetables such as broccoli, snap peas, sweet potato, carrots and cauliflower.
Oakley was on the Iams intestinal sensitivity formula because I tried taste of the wild ( of all kinds) and he was still having stool issues, combined with a puppy bout of giardia…he did well on it but I didn't feel good about the ingredients. From there I tried nature variety and he wasn't a fan. He has been sensative stool wise with many of the high quality foods so now we use Fromms and he is terrific. He loves all the varieties ( I mix two kinds at a time..one of their grain free versions with a grain version in order to get a reduced grain diet; stool issues if none or too much!)
His weight is steady and his coat has never looked shinier, smoother of softer. Lastly, he loves the taste and I don't have to coax him to eat.
I agree with not free feeding OR feeding from the same bowl. Since yours have issues (whether it's weight or sensitivity) knowing when they ate and controlling how much will allow you to better navigate around the health issues and possibly identify the cause of some as well!
