lulu is 4 months old, and has been on eukanuba puppy since i got her from the breeder. after doing my research (mainly here bc you people certainly know your dog foods!!) i decided i would go with wellness puppy.
last night, i began giving her a 90% to 10% mix of old food and new food. she LOVES the new food but less than 24 hours later, she has turned into a loose and rapid-firing poop machine! she has vomited once.
i have read about wellness causing diarrhea and also that any food change risks upsetting a little one's tummy. i am positive this is food related. lulu is in excellent health, up to date on vaccines, and her mood and energy level have not changed. she is 4 lbs.
soooo.....my question is...should i continue with what i'm doing as far as the mix? should i put even less wellness in or halt it and try again in a few weeks? she was having no trouble at all on the eukanuba, i just wanted her on a more nutritious food. at the moment, i'm feeling a little bad about doing this to her though.

. i really thought i was making a good decision but am now wondering.
thank you.