It could very well be that the new food you are giving them doesn't contain enough vitamins and minerals, and she is trying to get them on her own.
If you need to keep them on this food, buy a good quality vitamin supplement and give them that and hopefully that will help. Animals have a way of knowing what they should be getting and knowing whether or not they are actually getting it that is nothing short of miraculous. If they are lacking in a mineral they will eat some awfully strange things hoping to find it.
Rather than giving them a food for low-activity dogs, I would buy the best quality food I could afford (try to stay away from grocery brands, they're the doggie version of fast food) and I would feed her about half of what the directions called for. Monitor her body condition for a while to make sure she's not losing TOO much weight, and if she seems to be dropping too much, adjust how much you feed her accordingly. A good place to purchase premium foods is a feed store or an actual pet store as opposed to a grocery store. Most grocery stores don't carry premium brands, they all carry just regular grocery brands. Iams USED to be considered a premium brand, but now it's just an overpriced grocery brand. It's no better for your dog than any other grocery brand and it will cost you three times as much. You're much better off going to a feed store or pet store and buying a brand like Canidae or Flint River Ranch or one of those. Ask the clerk for some advice as to which would be a good brand to try. It will be pricey, but you'll only be feeding a fraction of what you would normally feed because the formula of the food is so much better.
Where you might be instructed to feed 6 to 7 cups a day of a grocery brand, a good premium brand would require you to feed about half that or perhaps a bit less than half. Another plus where it comes to the premium brand is that the digestibility of it is far superior to that of the grocery brands. It will cut down on the amount of stool your dog produces because the body actually uses more of the food instead of passing it out as waste.
Please keep us informed as to how your dogs are doing.
Ghilly