Alright, this might be a bit confusing.
I've got two terrariums, a large and small, that I finished setting up about 3 months ago. All the plants seem to be really happy... except the pilea depressas. Both seem to be losing leaves and breaking off stems near the tips and the leaves have become really pale. I investigated some more, checking around the soil to see whats going on. I inoculated both tanks with springtails and isopods as cleanup crew and both seem to be doing well, so I expected to see those. I also know both tanks have a fungus gnat infestation, though since every other plant in both terrariums seem to be fine I didn't suspect them. What I didn't expect was these tiny, tiny brown bugs that look like little brown mites absolutely everywhere. I dont know what they are but they're definitely not anything I put into the terrariums intentionally and definitely not gnat fly larvae. I'm worried they'll start to damage my other plants as well, though for now they seem fine.
I did my best to take a picture of them on a spoon (along with the setup of the terrariums and the pilea depressas) and hopefully you'll at least see the size and color. There insanely small and hard to get to focus in the camera. Also ignore the Chinese money plants - they were both transplanted from a larger plant that was already dying and I know now they aren't really suited for this terrarium which is quite wet. Maybe thats the se issue with these smaller pileas and not these little bugs?
Thanks for all your help!