Foot rot on my new millipede?

[Sooty]

Just four days ago I got my first ever millipedes and I'm worried about my N. Americanus. I thought at first that she had dirt on her legs, but upon closer inspection I think she might have foot rot.. She has been behaving normally and neither of her tank mates have it as far as I'm aware, but some of her legs look to be deformed or missing. Could any more experienced keepers confirm if that's what this is? I just want to be 100% sure she has it before doing anything drastic.

 

[Sooty]

Update: After comparing the symptoms of foot rot to what I've observed I've decided to go ahead and make a quarantine tank for Pumpkin. Tried to give her a shower and brush her with a brand new gentle toothbrush, but as it turns out millipedes react even the smallest bit of room temperature water with all of the hatred of a cat! I'm keeping an eye on the other two to see if they start showing any signs of rot, but they seem fine so far. Any tips on keeping a humidity that's bad for bacteria but still good for millies would be appreciated!

 

[Elytra and Antenna]

A lot of times they come that way from damage and regular wear and tear in nature. I have had it happen to old captive-bred specimens as well, but have never seen it transfer to a young animal.