*Looks guiltily at the kalimba sitting on her bookshelf.* I absolutely do not see what you mean. At all.
Reflective surfaces are horrible to photograph through and I have no tips. For the low light, is it because brightness might disturb the tarantulas? Otherwise, DIY photo light boxes might be of help and they are cheap-ish to make. Maybe try to put your phone on a stand/bean bag, adjust the focus (if your phone lets you), and set a timer, so the phone will not move while it takes the picture (if the spiders are very mobile, you might be out of luck).
