Millipede Deaths

[Anchoirnis]

I've had my millipedes for four months, and two out of six have died. I realize this could just be chance, as all are immature, but I wanted to post some details and see if anyone sees anything glaringly wrong. I'd really hate to cause another death.

The first that died was an ivory, and that was 3-4 weeks after I got him. He seemed active and healthy, and didn't slow down at all before his death. A friend handled him the day before, everything was fine, and then the next day, dead.
The enclosure is certainly large enough. At this point, all it had was fresh substrate, a small amount of calcium added, and some cork wood decor. I made sure the soil was damp and there's ventilation. I marked his death up to the stress of moving or the just chance.

Then, a second died yesterday, an Orthoporus ornatus. Within the past few weeks she's slowed down a bit and stared spending longer curled up, but has still be active and feeding and all so I didn't think anything was wrong.
However, the enclosure has gone through a lot of changes recently. I added plants about two weeks ago (after she slowed down, so not the catalyst), a fern and a fittonia. Additionally, I've been having a problem with gnats in the tank, and have been trying parasitic nematodes. I was told by other hobbyists that they were totally safe for millipedes, but I'm also worried I over watered the enclosure to get the nematodes to work? Would that kill a millipede?
Additionally, the same friend who held the ivory held the ornatus two days before which REALLY sounds like murder but I was there and can confirm no murder took place but like. Millipedes don't have adaptive immune systems they can't be allergic to a person right lol? The ornatus was dropped a small distance but it didn't do any exoskeleton damage, could that have skill killed her?

Since I've discovered the second death, I've only seen one of my remaining millipedes as the others are more reclusive, but I can confirm at least one is still alive lol.

So. Anyway. Ideas? Did the ghats kill my millipedes? Was it chance? Is my friend a millipede toxin? Am I unfit to have bug children? Thanks for reading my fear induced ramble. I made an account for this.

 

[BepopCola]

Did they smell dead?
Gnats won't cause a quick death like that. Overwatering could kill, I'm not sure if it'll happen that quickly, but if you take a fist of the substrate and squeeze it, does water drip out?
Does your friend use anything on their hands, like lotion? Any chance of residuals leftover on their hands, like chemicals from car detailing or something, or did they hold any pets dosed with flea medicine?
As for the fall, about how far did the millipede fall and what did it fall onto?
Have you fed them any fruits or veggies?

Also, what species are the remaining 4 millis?

 

[BepopCola]

I double posted somehow! How do I delete this one?

 

[Humbertosvaldes]

I had a ton die. They sucked. Smell. Pretty as hell and active but....

 

[Polenth]

Ideally, don't let people hold your millipedes. If you really must let someone hold them, make them wash their hands properly in plain water (so two rounds of happy birthday in time and making sure to wash the whole hand including between the fingers and under the nails). Millipedes should be held close to a soft surface, so there's little to no risk of a fall. In other words, things on people's hands and falling can absolutely kill them.

It's hard to say about the enclosure without seeing it. Make sure to include a side shot showing substrate depth and a shot of the lid showing the ventilation.

Fungus gnats aren't a problem. Same goes with fruit flies. They annoy people, but that's not the same thing as harmful to the animals. You can usually control them by adding springtails (which outcompete them and keep down numbers), though that option is out for you now.

The nematodes are not something I'd recommend people use in homes with invertebrate pets. They're not totally safe with millipedes, but the risk is generally considered to be low. However, they will eat springtails, beetle larvae and other insects. Unless a biological control is very specific to particular prey, it can easily get out of control.