I'm sorry that he died.
Looking at your other thread and your latest reply, you may be dealing with a respiratory disease. The coughing and runny nose doesn't sound too good.
You have consolidated birds together - is there plenty of ventilation where you are housing them now? Could excess...
What do you feed including treats?
I would check her crop to make sure it's emptying and also look inside her beak for any lesions or canker.
If her crop is squishy, hard, doughy, etc., then I would begin treating her. If possible, place her in a kennel by herself with just water for the day...