Spider mites don't do anything harmful that I know of? But can become numerous.
I'm not sure what your experience was with them but for me it was bad. I had no webs or huge outbreaks . Still they multiply fast, you have to stay on top of them all the time. Even then they took my Cocoa OG down. I will admit the other strains were not as affected by them but all strains suffered yield damage and fucking shit load of extra work. The name of the thread kind of speaks to what people deal with.