Soft stools with 5yr old dog?

My rottweiler started getting diarrhea with her old food, i took her to the vet who said she had a tummy upset and gave me some tablets for a week while she ate some chicken. So before i got these tablets i fed her on beta adult and pedigree chum, i ran out of her beta food the day i took her to the vet, and she told me to give her chicken for the tablets week anyway so during that week i found out how crap beta and pedigree chum is so i ordered in some ORIJEN pet food. I didnt want to buy more beta considering it was crap, even though i know i should have mixed it slowly. Her stools are actually a lot better than before they are formed but still very soft. I know i've been messing around with her diet too much, but instead of going back to beta and messing all around again i'm just feeding her the recommended 400g of orijen a day and avoiding meat for the time being and i think i'll introduce her some chicken or tuna after a couple of weeks again, i gave her slightly more the other day and she was sick a little bit, basically what i'm asking is...will this soft poop go away when her system gets used to the new feed (considering it was introduced a lot faster than you should) and how many days should i give her feeding the ORIJEN to know if it will suit her in the long run. The thing is she's pooping twice a day..which is much more regular than before its just very soft. Many thanks for your advice