Need ADVICE ASAP!!!!

[rg_girlca]

I have taken on 2 kittens, brothers, ages 3 1/2 months old and weigh 4 1/2 lbs. each. They will be 4 months on the 30th. The girl that had them, is a young student, who at the moment is working 2 jobs. A friend of a friend. She leaves in the morning and doesn't get home until around 11:30 P.M. She took in a stray mama who had 5 babies. Was able to find homes for 3 of them. She and her roomate decided to keep mama & 2 kitties. Got too overwhelmed with coming home and having to clean up the litter box and vomit most of the time. I was concerned when she told me about the vomiting and asked what she was feeding them. She would either buy the Wal-Mart brand or any other brand that was on sale. She figured they would prefer a variety of foods. She asked if I could take them until she finishes her first job on the 30th of August. I've had them now for just over a week. She was feeding them Purina Cat Chow at the time. I bought the Purina Kitten Chow and started to introduce them to that. I brought them to the vet on Monday, for their first checkup and shots. Mentioned to the vet about the vomiting and he said to buy a food for sensitive stomachs. They didn't vomit for 3 1/2 days, so I assumed that the kitten chow was helping. NOT!!!! They vomited again on Thursday and then again yesterday. So I have taken them off the dry food and gave them a bit of Friskies wet since that's all I had at the time.
What I would like to know, if anyone else has had this problem with kittens and what brand of food do you recommend. I also found out yesterday from the girl that the mama cat was also vomiting. I find it very strange that all 3 should have this problem. Do you think that it could be something else, besides the food? Apart from that, they are normal little kitties. Full of vim & Viniger.
I'm sorry this is so long, but if anyone could give me some good sound advice, I would really appreciate it.
They stay in my room, because I have 7 cats in the house, 1 dog and another little rescue girl of 11 weeks, who will be going to her new home next weekend.