The kitten in question is of the mama cat about whom i have written in the above question. She refuses to eat. Drinks water but goes on to sit in water or cold places. She is getting weaker. Its 18 hours since she has eaten anything. Nearby vets aren't available too due to public holiday. Kindly advise. Its 10 weeks old.
Sitting in water = it is feeling too hot. Most likely it has a fever. This fever could be due to an unrelated illness, or stress over the mother's death, or the same infection/poisoning that took the mother and transmitted through saliva or milk. Hopefully it is not serious.
As a first step, try measuring the internal body temperature. Search YouTube if you don't know how (the anus is the easiest and most reliable).
Second, use a syringe and feed it with oral rehydration solutions. It is a mix of glucose/dextrose and essential salts. Also try giving small amount of liquid kitten food or diluted cow milk with the syringe and check that it doesn't vomit it back out.
Third, try to consult an actual vet online via video. If they are nice enough and good at their job, you can get a preliminary diagnosis without a physical visit.
If there are no vets available try asking a vet medical store. Sometimes the store pharmacist can be very helpful in a pinch.
If the vet recommends an antibiotic injection, maybe you or someone nearby can administer it intramuscularly without waiting for the hospital to open. Get the ratio and quantity right if you choose to administer the injection yourself.
Act fast. Kittens can die quickly.
I used to work for a feline veterinarian. First you have to get some food in her. Most cats can't refuse baby food of the strained meat varieties. ( all meat ) I would feed them with a syringe and as they improve you can try putting it on the side of their jaws. They will clean it off and in the process eat the food.