Can you send one to a necropsy lab in your state? They'll be able to tell you what they died from.
https://www.heritageacresmarket.com/poultry-necropsy-labs/
I'm not familiar with CA quail, but the feed is definitely not right. They should have 28-30% protein feed.
As for the temperature, the numbers don't mean as much as how the chicks are behaving. Are they huddled together, climbing over each other? Are they spread out, laying flat, and...