Cockatiel sick from last 5 days

by Tripti Khare
(Mumbai, India)

Cockatiel sick from last 5 days, nostrils clogged, running poop, sleeping alot and not singing, eating or dinking.

We brought a small 8-9 month old cockatiel from a filthy pet store 4 months he was fine active and affectionate bird till 4 months but now he is seriously sick,and we dont have avian vet here in mumbai (India)
Symptoms:
1) Not speaking,eating or drinking at all
2) Clogged and sore nostrils and sneezing alot while scratcing nostrils by his claws
3) Fluffed up, dull and sleeping all the time
4) Runny watery green(like pee soup) poop
5) scratching in the feather with beaak alot (I looked for lice but cudnt find any)

From two days I am feeding him grinded seeds & vegetable paste(Cucember, peas, carrots and sunflower seed) and water throgh a syringe (needle less) though he doesnt want to eat at all but I feed him a little forcefully :( because he is loosing lots and lots of water while pooping and used to look so so weak after me feeding him like this he doesnt look weak but all the other symptom remain same.
Please please please help me.