I think a lot of breeders feed Pro Plan because of the incentives from the breeder program. I'm sure it works fine for some dogs, but I bet a lot of them are like yours that have soft stool and various other issues that the breeder or owner perceives as "normal".
For your girl that needs to lose weight I'd recommend a higher protein food. A lot of times the foods high in protein and low in carbs will help a dog lose fat and put on muscle. For her I would try the new grain free food from Wellness- CORE. It's higher protein than most foods, but not the extreme amount as in EVO and Nature's Variety Instinct. Those foods have 42% protein and 22% fat which I feel is VERY high. EVO has a high ash level also- 12.38% and it's usually recommended not to feed over about 8%. It works for a lot of dogs, but I've heard too many cases of previously healthy dogs having abnormal kidney and liver levels after eating EVO for awhile. The high fat affects the liver and the ash and protein affect the kidneys.
Regular CORE is 34% protein, 14% fat. I like that it's not too extreme. I'm trying to remember the ash % off the top of my head, if I remember right it's 7 or 8%. For your girl the reduced fat CORE would probably be good. 33% protein, 9% fat. Here's a link to that food:
http://www.oldmotherhubbard.com/well...n_reduced.html
For your boy I would recommend either Wellness CORE or Eagle Pack Holistic. My dog has had the softest coat on this food (out of countless holistic foods). One of the things I love about EP Holistic is that it that the heat sensitive ingredients like probiotics are added after the cooking process. I really can't say enough about the food.

I'm REALLY picky about ingredients and Eagle Pack Holistic has all of the ingredients I look for and none of the ones that I avoid. I think any of their holistic varieties should work for your boy. Here's a link to their website:
http://www.eaglepack.com/Pages/HS_Dog.html