Try spraying some Garlic Spray onto it. I do NOT advise making this in a small, confined area! It's potent stuff. But it's good for a lot of plant diseases and insect infestations. Sage really isn't happy indoors, you know. A healthy plant doesn't usually have a problem fending off a few bugs, but a sick plant will encourage plagues! If you can possibly give your plant a holiday outdoors for a while, other helpful bugs will help in the healing process. And don't forget that light filtered through glass is NOT the same as direct sunlight!

GARLIC SPRAY:
Soak 1/2 cup crushed garlic cloves in 1/2 cup vegetable oil for one week. Add a little liquid soap and dilute the mixture - 1 part mixture to 10 parts water. Garlic spay will kill and repel aphids, woolly aphids, bean fly, stink bugs, crickets, grasshoppers, red spider mite, sawfly larvae, scale, snails, slugs, thrips and caterpillars, mosquitoes and ticks, the adult moths of leaf-miners and mealy bugs. It is an effective fungicide when used 3-4 times a week against potato blight and damping off.
OR
Crush 100g garlic, 2 chillies and 2 onions and cover with water for 24 hours. Strain and add enough water to make up 2 litres.

Making garlic spray might be tricky in a dorm room I don't know what setup you have. You might be describing thrips, or possibly aphids. Thrips are a bit tricky and I don't have a lot of experience with them, but I think you could use a horticultural oil or neem oil for an organic edible solution. You can find premixed sprays of these things at HD or Lowes.

Back on September 13th, I brought in my sage and lavender for the winter. I live in a 5th floor studio apartment with no balcony (the apartment gardens are outside the building). The sage is in a 5 gal bucket, the lavender in a 5 gal pot. I used store bought potting soil, and a little organic fertilizer. They were doing great, as they were sitting atop my unused radiator getting full sun from a wide open window, but then I had to move them to the floor at the beginning of October because the radiator was to be turned on.

I watered them a day or so after I moved them, about half a gallon per plant, or a little more...which promptly drained out onto my floor. Since then the sage has been developing brown spots on its leaves, had little black gnatlike bugs, and also had some webbing (indicating spider mites I believe). I've been removing it all as it comes, but the plant doesn't seem to be bouncing back. I haven't watered it or the lavender since.

I realize the sage isn't happy indoors, but I had some good reasons for bringing it in, namely a neighbor who was watering it every day (despite repeated 'mind your own business' type warnings), the seriously cold winters here, and that I needed to move it to another spot anyway (its my first garden, so I made some booboos!) Next year both will stay outdoors, tho. The lavender, on the other hand, is obviously happy, and has put on the most growth its ever had (reference above neighbor for why it stayed small).

Is there anything I can do in my very limited space and VERY limited budget, preferably with household stuff and/or organically? Would the flourescent light fixture I bought last week at a garage sale help make the sage happier and help it bounce back?