I think that's the same heat plate I had for a day before I threw it in the trash. It was getting WAY too hot.
I'd use a regular light bulb on a clippy lamp if I were you. It's what I use. I have 3 day old quail now with just a regular old school light bulb keeping them warm.
I don't think...
1. This heat plate thing picture is what you are using?
2. Is this picture the comfort heat mat you mention?
3. Can you post a picture of the brooder the way it looks right now? I'd stop feeding quail eggs and tuna immediately.
4. The crumbled feed...did you hammer it up to make it small...