I'd consider removing any that behaves or looks odd. If they have some kind of pathogen, removing them soon enough might help curb or prevent spread of whatever, if there is something.
I had some younger ants that were dying off for unknown reasons(color changes with age in these) and i noticed an oddity coloring in their gastors. I started removing any that were younger than seemed right to be doing foraging work, and any that i though looked funny in the gastor in any way.
I never got any answers about anything. Maybe there was no problem and i just killed a bunch ants for no reason.
But the colony is here today and i've not continued to have the young ant death issue.
Do keep a close eye on what you feed them and what might be getting into their habitat by just drifting in on the open air, like say window cleaner if the nest were near enough window being cleaned.
Even small amounts of some things can be dangerous to them in the enclose environment where they can't just move off and not go into a bad area.
Be sure and give flash boils to feeder insects to protect against mites or other parasites that could be introduced.
And only use organic fruits or whatever as sugar sources to avoid pesticides.
Be wary of even the most cleanest organicest labeled honey. The conditions on the honey farm that earn that label are not able to bee imposed on the bees who fly where they dam well please and bring back whatever from wherever they go.
I've not trusted to any honey for my ants because of this and keep to organic fruits and berries, and commercial or homebrew sunburst.
best of luck.
