Is she pooping outside the litter box while you are at work as well or just when gone overnight?
Do you still have the 2nd litterbox? Some cats prefer to pee in one & poop in another, this is a habit that can be picked up at anytime even if they've never done it before. I would allow access to both boxes either in the same room or in different areas. Try to clean the boxes out as often as you can - right after she's gone if possible, with a full litter change & box cleaning at least every 2 weeks. The cleaner the box the more likely she'll use it rather than the carpet.
Clean the carpet area very well with an enzymatic cleaner that doesn't have harsh chemical smells and no ammonia, Nature's Miracle is a good one. You can also make a spray bottle of homemade cleaner = 1 cup of water + 1/4 cup vinegar + 1/4 Isopropyl rubbing alcohol spray the area well, blot dry, re-spray & let dry.
Once the area is clean if you see her heading to that area you can try putting the 2nd box on the spot she's been pooping.
Have you taken in a poop sample in to the vet to check for worms?
Is the consistency of her poop firm & solid but not hard & dry or slimey & squishy?
A few words on the food, honestly that is not a good food, have a look at the ingredients, lots of fillers - corn gluten meal, soybean meal, whole grain corn, brewers rice - what nutritional value is that for a carnivore? Or anyone really?
Even we don't digest corn very well.
There is little actual named meat - "animal digest" "animal fat" "poultry by product meal" no one but the rendering plant knows what those actually are - what kind of animal does animal fat come from? Is it beef, chicken, lamb, pork or something else?
Cats should all be eating (ideally raw but not everyone is up for that) canned food not dry food, there is not enough moisture in the dry to keep their kidneys healthy among other organ systems. Cats have a special moisture recycling system within their bodies that is fairly unique (humans, dogs & most other animals don't) so when the main portion of their diet is dry food they are not ingesting or retaining enough water to supplement and refresh their systems. A raw or canned diet is roughly 70-85% moisture whereas a dry food is between 8-10%, they cannot drink enough to supplement.
Have a look at
Wellness canned food, you can see the difference in the ingredient list alone.
Some other good brands are
By Nature,
Nature's Variety Instinct,
Merrick's Before Grain