seeing all you are doing for your littles I know you have best intentions for your them, and they will be happy and well taken care of. GOOD LUCK :thumbsup
Sounds like temp under is 91 that should be fine. They will do the rest on their own they know where they like it. With the plate on an angle, they will regulate how close to plate they feel comfortable with. I have never used brooder plates, but they can be good in warmer areas most tend to...
Now you can fully see what I was explaining about the 250-watt bulb indoors in a smaller space. If I brood indoor I use lower wattage bulbs, I like 175 watt or less for indoors. You can even get them even lower in reptile heat bulbs.
One other thing that will help with the other chicks now and for future for quick stress relief is Poultry Nutri-Drench it gets them up and going faster than anything else I have used.
You have received some good advice and info hoping everything goes well for you and chicks from here on out. Don't be afraid to ask if you have any other questions there are some very knowledgeable folks on here more than willing to help. :thumbsup
I am just looking at your setup and making observations as you asked for HELP and trying to give you good tips. Have you checked temp in coolest area in box?
Maybe the hatchling you received in past didn't have as much shipping stress as these have endured and was able to handle the little bit the heat stressed them if it is even the heat and not just shipping stress alon.
Also see they are not all the same and that may also affect amount of stress those different birds can handle. There are so many factors that would affect how much stress a particular hatchling can handle.
The amount of stress affects everyone differently and some don't like as much heat and may affect them more than others. A few may have been more stressed from the beginning making them less able to handle any more stress.
If the tote isn't much bigger than that little box, then I would find a bigger box. They do need the 90-95 area, but they also need a much cooler area. Thats a 250-watt heat bulb they put out a tremendous amount of heat especially indoors. Very hard to get a small area heated to correct temp and...
Also noticed brooder box is very small and doesn't look like they have much room to get away from heat. They need a spot at the 90-95 mark but also need an area much cooler, if the whole brooder is 95 degrees it can be a problem.