I only used chick starter feed
Should be no air pollution in our bathroom
No sprays
The feed is new
I cleaned the water 2 a day sometimes 3 if I was home all day.
The brooder is definitely warmer. Maybe too warm. I don't have a way to get the temp but any time I felt it was a bit warm I would raise the lamp just a bit more. Because they definitely would not hang around under the brooder
First, I'm so sorry for your loss! that is heartbreaking.
I can help with determining the temperature. A good way to get the temperature -purchase a meat thermometer. You may already have one in your kitchen. Dial type thermometer that goes from 0F to 220F with gradations of two degrees is what you want. Picture example below. They have these at any grocery store that sells cooking implements, like
walmart or
amazon.
Oven thermometers and candy thermometers don't go low enough but meat thermometers do, and it's stainless steel so won't corrode when in contact with droppings or moisture, also super easy to clean. Place it in the bottom of the brooder directly under the heat lamp on top of the shavings. Let it sit there for a while until the temperature stabilizes (15-30 minutes ought to be plenty). Then you'll know what the max temp is that your chickens would be/were seeing as they walk/walked directly under the heat lamp. I've found with the lamp in the same place and all other things being equal that my brooder can vary 10-20 degrees depending on room/ambient temperature and conditions.
Also this will help you figure out if the walls of the brooder are/were getting too hot - if you set the thermometer right next to the brooder wall, or tape it to the hottest place on the wall of your brooder it will let you know the temperature your brooder wall is being heated to. You want at least 2 inches of the stick perpendicular to the beam of the heat lamp at your measurement location - don't tape on top of this two inches if you can help it.
Different types of plastic outgas different chemicals at different temperatures. A google search on softening point and/or melting point for the material your brooder is made out of (if it's fiberglass, polycarbonate, plastic, rubber, etc.) will tell you how hot is too hot for the material - you want to stay below the softening point, or at less than 2/3 of the melting point temperature if they don't give a softening point. Also you might check Google to see if there's a mention of any offgassing the material would do and at what temps. [For those who brood in plastic/rubber tubs, the manufacturer, or in the USA, the recycling symbol they stamp on the bottom of the plastic or rubber tub, will tell you what material it is.]
For a shower brooder, the manufacturer should tell you what your shower body is made out of. Did you have a shower curtain near the chicks? Was it used/had deposits on it from being used, or were there any hard deposits elsewhere in the tub/shower? Shower curtains can be really bad about outgassing/offgassing when new, and who knows what chemicals from the deposited soaps or soap scum could be released upon heating. Not trying to knock your tub cleaning abilities at all - it can be hard to even see the stuff, much less get it all off.
Also as a last thought, do you guys have black mold? Cause it could be down in your drain and you not know. I don't think black mold would have killed so many chicks all at once, but if you hit the offgassing point of some chemical particularly toxic to birds and didn't have enough ventilation to move the gas out, that might have done it.
I'm so sorry for your loss.
