My cat has viral infection and I need urgent assistance

Hi, I adopted three newly born street cats after 5 to 6 months one of my cats stop eating with vomiting and bloody stool and start losing weight. I quickly go to the doctor and the doctor gives me a drip with a different antibiotic but the cat didn't make it and this infection spread to the other two cats and did same but two cats died in just two days but one of the cats is strong but infection didn't stop. The doctor continuously gives a drip for three days but can't improve still getting worst. 

Symptoms:

Cat didn't eat (We use a syringe to feed water and protein)

continues watery motion same as food after eating (Blood is stopped after drip)

Cat losing a lot's weight

Vomiting also stopped

Very bad small but not as cat poop

Food and medicine we are using.

Food

ORS (After every one to two hours)

Cerelac Pomegranate

Boiled Chicken to feed using a syringe

Medicine:

flagyl

Smecta sachet

Enterogermina

I need urgent assistance

Thanks