As egglayers hatch out with little to no color, the first livebearer species that comes to mind that could be solid orange/red from birth is a red Swordtail. But that begs the question: Where was the mother? Unless, some the the plants had been in a tank with a female who had given birth and when the plants were moved, they took a baby with them. Trying to play "Guess the Species" under the conditions you described could indeed be difficult. If you are really curious, perhaps the shop would agree to catch it from the plant tank and place it into a small clear container for close examination.

The article below was linked on the Bird Forum as a possibility. tj Here is a link that might be useful: Ark Die-offs

I know two people who have this problem, one found the cause and the other is still unable to find the source, after 5 years! Yuk! The first one had put out Decon as she knew she had mice. They will leave the house in search of water unless they are able to find water in the house. The mice had built a nest in the air duct run behind the furnace hunidifier and had several litters. They died when the furnace was turned on for the winter, only to become Crispy Critters. When ever the furnace fan kicked in the smell was there. The second house has never been able to find the source but is only there when the furnace is on. They have had the ducts cleaned, the furnace taken apart etc. This has been ongoing for 5 years. I would tell you husband to take another look at the fireplace. When you open the damper to sniff, the air pressure is changed and the smoke and the smell is going to rise. There is a shelf above the damper, to the back and you may have something dead, rotting on it. Just take a counter broom or a shop vac and see what you are able to find. Squirrels can get through the cap at the top so unless your husband has been up on the roof, he might want to check that out also. Good Luck!

Don't you know what formaldehyde is? It's the chemical used to embalm dead people or animals. It's used, in very tiny amounts, in various things, but if it came from a ceiling fan in a place you are renting rather than owning, you could have a case for breaking your lease immediately (and anyone with children would do so). But it's also important in fact for you to prove it by getting a certified inspector in to verify that's what happening. You can "research" til the cows come home on the internet but it's not going to help you legally, whereas an inspector's written report will. In any case, get your daughter out of there (if it's not obvious that it should happen), but also don't ignore the fact that she could be sick from something that has nothing at all to do with where you live.