Bug problem

Stupid question...what damage does spider mites do to a plant? Ive neer seen one so dont know what one looks like but did see a very small bug crawl accross my view screen when loking at one of my buds. The plants are doing fine except there are small discoulored spots on the leaves. Im about 4 weeks from harvest.

Spider mites make webs and completely kill plants. Likely aphids you have. They can kill plants too. A pyrithrin bomb will take care of it.