Hey dude - I'd really need a pic of this to know exactly what you're dealing with. Could be mites, could be aphids, could be a number of things. Neither of the above are a good thing and you gotta jump on insect issues quick if you want to avoid utter disaster. Some general options for addressing the problem include (by order of effectiveness);
1. Neem oil treatments (all natural)- find yourself some neem oil and dilute it in water. Shake/mix well and spray this solution on the entirety of the plant. Maintain treatments 1-2 times a day until the problem seems to have rectified itself and none of the little bastards remain. ***Do not use this method during flower if you can avoid it. This stuff will ruin the scent and taste profile of your buds and while smoking weed isn't exactly healthy, smoking weed with neem oil on it is worse. If you ever smoked "soap sprayed" weed back in the day - this is probably what you were tasting.
2. Predatory insects (all natural)- every pest has it's own predator and predatory insects, in large amounts, are simply more effective than neem oil treatments. You can purchase pred. insects like lady bugs in batches of 500 or 1000 online or sometimes at a local gardening store. These girls look pretty, generally don't cause any harm to other parts of the house and they LOVE aphids and mites. You set these things loose in your tent and within a couple of weeks you will see a huge difference. In combination with aggressive pruning/defoliation, you should be insect free.
3. Chemical feed treatments - I can't give you a name for this treatment but any good local hydroponics shop should have it on offer. Effectively a chemical additive that you put in your feed water. The roots take up the chemical and when the insects feed on the stems or leaves they effectively take in the poison and die. This particular "chemical" is supposed to be non-toxic and safe for humans but it is VERY effective at eradicating insect pests. You'll be pest free within 24 hours. Again, forgot the name of the stuff and it won't be cheap in comparison to the 2 options above but it will also be the most reliable fool proof solution.
Hope the options help and ping me if you've got some photos so that we can drill down to exactly what the problem is. 👍