Should I switch from ACANA Singles to Zignature LID?

[Samantha & Charlie]

Up until a few days ago, Charlie was doing great on Acana. Lately though, he's been having horrible diarrhea and threw up twice on Thursday (food wasn't digested). On Friday, he had no diarrhea and didn't throw up (I had him on a chicken and rice diet). Today, the diarrhea came back, but he's also sensitive to chicken, so that might be a factor why his stomach is still upset. He's been acting fairly active as well. But someone suggested to try the Zignature line, and I thought kangaroo might be a good meat to try out. Any advice on this brand?

Could he start having issues with a food brand after being on it for 8ish months?

[Karen, Jasper and Jackdoodle]

I had another thought about the lack of stool. The homemade diet has very little residue, so dogs typically produce less stool on them, and they're very low in calories due to the high moisture content, so you have to feed about twice as much as you do kibble. He may not be getting enough bulk or food to form stool.