What did I do wrong?

[Mechanic3089]

I had a colony of horse ant. Queen, around 40-50 workers, brood at different stages. The colony seemed to be doing well, ate well had plenty of water and the occasional bit of honey. Then, workers started dying, didnt think anything of it at first, then more started dying at a alarming rate, then the brood started dying, newly enclosed ants would die a day later, larvae would die and the eggs would turn a funny yellow color and just never hatch. This all happened over the course of a month, trying to change their diet to see if anything helped. Today, the last of the workers died and the queen is the only one left. What did I do wrong? Can I rebuild the colony with the queen being out of the founding stage? Should I just let the queen go? Any advice would help

[TEXASantlover]

Just my advice but I haven’t founded a colony yet.
Isolate the queen away from the formicarium (or whatever they were in) incase it is a fungus or mite plague. I have had similar experience when in the founding stage where the eggs die. Usually a sign of fungus/mold or something environmental.

[Hawkeye]

I had a colony of horse ant. Queen, around 40-50 workers, brood at different stages. The colony seemed to be doing well, ate well had plenty of water and the occasional bit of honey. Then, workers started dying, didnt think anything of it at first, then more started dying at a alarming rate, then the brood started dying, newly enclosed ants would die a day later, larvae would die and the eggs would turn a funny yellow color and just never hatch. This all happened over the course of a month, trying to change their diet to see if anything helped. Today, the last of the workers died and the queen is the only one left. What did I do wrong? Can I rebuild the colony with the queen being out of the founding stage? Should I just let the queen go? Any advice would help

Sounds like an environmental issue like a fungus/mites or a contaminant in the food supply. Though the latter seems unlikely as that would affect the queen too.

In any case I would quarantine the queen in a clean test tube setup as soon as possible. Whatever it is that was having this negative effect on your colony, you don't want to expose her to it any longer than necessary.
Your queen can eat and drink on her own, so no worries there. It is just more effective when the workers feed her, so she can concentrate on laying eggs.
The jelly from wet cat food is an excellent source of protein which she will likely need at this point.
I would not recommend setting her free at this point, as her chances of survival in the controlled circumstances of a test tube setup are much bigger.