I adopted a 2 year old chi about 3 months ago. She had several vet visits after the adoption and was deemed healthy at each visit. She is a tiny at just 3.5 pounds. About 5-6 weeks ago she had a single episode where she vomited up all her food during the wee hours of the morning and then she had liquid poop the day following. She stayed away from her food for a day and then went back on her food and all was well until last night. Fast forward 5 weeks or so and she did the same thing last night - vomited up all her food, has upset stomach/poop all night and this morning she won't eat or drink. Since the first time this happened I have noticed a decline in her overall appearance and mannerisms - she looks more frail, doesn't play with toys anymore, has lost weight and coat luster, and just sleeps all day and doesn't look healthy. She is on Wellness food and has been since adopted. She can barely get strength to walk. I adopted a healthy dog so I'm wondering what I am doing wrong that is making her unhealthy. She will be going to the vet this week, but I wanted to see if maybe someone has had a similar experience and has an opinion on possible causes.