It follows from the description, that they are indeed spider mites. Their development is favored by dried air heated by radiators. The most effective way to get rid of insects, by giving them a 10-minute cold shower. The stream of water must be directed to the underside of the leaves (bottom to top). So as not to wash out the ground, you can wrap the pot with a foil bag. The treatment should be repeated after a week. If you do not have small children and pets at home, and the pest-infested plant does not stand in the bedroom, it can be twice – in space 7-10 days – water 0,1 proc. Decis solution 2,5 EC.