They don't seem to be doing too much harm? Why, are they relaxing on sun loungers soaking up the rays from ur grow light lol. If u have spider mites (webs are a big indicator) they WILL do harm. Their re-production rate is astronomical an they will suck the life outta ur plants. Use Neem in future IMO as it does the trick. Wait 4 a better reply to deal with the ones u got now