Ok, if you're sure its spider mites the following is out of the FAQ section.
Spider Mites:
Signs of an Infestation:
Mites will first be noticed by the presence of small, discolored spots located near veins in the leaves. To see them, you will need the help of a 10X loupe, or a 30X Microscope. Mites use piercing mouthparts to suck sap. Mites will slow growth and attack the buds in advanced stages. The life cycle of the spider mite is closely tied to the temperature of the grow room; slow an infestation by keeping temp in the low 70?s.
Eliminating spider mites:
A No Pest strip is very effective in eliminating them. Avid is a very effective systemic chemical control. A soapy spray will also keep their numbers in check (thoroughly coat underside of the leaves). Space plants out to minimize transfer movement between plants.
And some more.
Spider Mites
Spider Mites
permalink
IDENTIFY: The spider mite is the most common pest found on indorr marijuana plantsand causes the most problems. To a newbies, they are hard to spot, spider mites have eight legs. Find microsopic spider mites on the bottom of the leaves. However, their telltale signs of feeding, yellowish white spots, on the tops of leaves are easy to see. Careful inspection reveals tiny spider webs on stems and under leaves as the infection progesss. A maginifying glass will help you see the yellow white two spotted, brown or red mites and their clear eggs. Indoors the most common is the two spotted spider mite. After the they fuck like rabbits females are fertilized for life and reproduce 80% female and 20% male eggs, females will lay about 100 eggs. (poor bitch)
Damage: Spider mites suck life giving sap from marijuana plantscausing over loss and stunting of growth. Leaves are poked with suck hole marks in yellow from failed to produce chloraphyl. The marijuana plant will loose partial to full function (which means your marijuana plantsare fucked) Leaf yellowing and drop. Once a plant is overrun with spider mites the infestation pregresses rapidly.
In simple words if you get mites and dont catch them you are screwed.
How to control Spider Mites: Be clean. This is the most important first step to spider minte control. Keep the grow room tools spotless and dis-infect your tools. Mother marijuana plantsoften have spider mites, Spray mothers often with miticides including once three days before cuttins. Once you become infested the entire grow room will have to be stripped down and clean. YOU DO NOT WANT THESE THINGS 
A little something I googled from the internet:
Control Strategies
Early detection of spider mites, before damage is noticed, is important. The tiny spider mites can be detected by taking a piece of white paper or cardboard and striking some plant foliage on it. The mites can be seen walking slowly on the paper. If 10 or more mites per sample are common, controls may be needed.
Option 1: Cultural Control - Syringing Since rainy weather seems to knock off spider mites, using a forceful jet of water from a hose (syringing) can perform the same task. A regular syringing can keep spider mites under control on most ornamental plants in the landscape. This technique also helps conserve natural predators.
Option 2: Cultural Control - Quarantine and Inspection The twospotted spider mite is often introduced on infested bedding and house plants. When purchasing new plants, carefully inspect the lower leaf surface for any signs of mite activity. New house plants should be quarantined from other plants until you are sure that no mites are present.
Option 3: Biological Control - Predators There are numerous insects (lacewings and lady beetles) that prey on spider mites. However, the most commonly sold predators are other types of mites. Predatory mites (usually Phytoseiulus spp., Amblyseius spp. or Metaseiulus spp.) can be purchased and released onto infested plants. Be sure to check listings to determine which species is appropriate. Some species are host specific and each predator works better under different weather conditions. If predators are used, do not apply pesticides that will kill them.
Option 4: Chemical Control - "Soft Pesticides" Most spider mites can be controlled with insecticidal oils and soaps. The oils, both horticultural oil and dormant oil, can be used. Horticultural oils can be used on perennial and woody ornamentals during the summer at the 1 to 2 percent rate. Higher rates of horticultural oil (3 to 4 percent) or dormant oil are useful for killing mite eggs and dormant adults in the fall and spring. The insecticidal soaps are useful in the warm season. Remember that mites are very tiny and soaps and oils work by contact only. Therefore, thorough coverage of the plant is necessary for good control.
Option 5: Chemical Control - Miticides Spider mites are usually not killed by regular insecticides, so be sure to check the pesticide label to see if "miticide" is present. Pesticides claiming "for mite suppression" are usually weak miticides and will not perform well. There are few products available to the homeowner. Dicofol (=Kelthane) is registered for over-the-counter use but is difficult to find. Acephate (=Orthene), dimethoate (=Cygon), chlorpyrifos (=Dursban), diazinon, disulfoton (=Di-syston), and malathion have over-the-counter product labels but are considered weak miticides.
I believe that the "oil treatment" that is written about above (soft treatments) is Neem oil - that may help out.
I really hope you get these things under control with out the use of chemicals - good luck my friend.
Peace