The spotting is by the Four Lined Plant Bug, common pest of mints.

Hi and thanks for the responses. The cutting is in a different batch of soil than the original, however I have maybe a half dozen other plants in this soil or a mix containing this soil and they haven't shown signs of any diseases. I'll try rinsing it, it is a very small cutting. It's growing a lot slower than mint has grown for me in the past :/ I live in the city, not very close to a nursery but maybe someone at the farmer's market will be able to help me out! Thanks a lot :)

Thanks, rhizo_1. I really hope it isn't leaf miner. From what little I read online, it seems to be harder to get rid of than aphids (and more insidious). I tried holding the leaves up to light, but they were too withered to get a good view. I have a peppermint plant near the mint that doesn't seem to be affected yet. I guess I will be moving the peppermint to another window. Any suggestions for getting rid of the leaf miner on an indoors plant besides neem oil or wasps (which isn't an option)? Would regularly plucking off the affected leaves help? Also, is it possible the leaf miner originated in my home or was it there in the plant when I purchased it? Unfortunately, by the time I got my mint home it was suffering from shock - it took me a while to get home and the mint was not happy in the plastic bag I had it in. It took about 2 weeks before the mint was back to normal and before I realized the affected leaves were not the result of the shock but a pest.

Yeah I think you're right about the white; looked again today and it was gone. The scale on the last plant if there is subtle, but how about the numerous non-subtle brown spots, some of which look eaten into the leaf? Some kind of mite? If so, here's the combo I've come up with: Acephate - Amazon: "97UP 1lb bag Generic Orthene Insect & Fire Ant Killer" - http://www.ext.colostate.edu/pubs/insect/05507.html says "Insecticide with some effectiveness against spider mites. Systemic." Forbid 4F - eBay: "Free Forbid 4F Miticide Spiromesifen 1/4 OZ free gift when u purchase 3 pipettes" - "Like Avid, it is translaminar. The active ingredient, spiromesifin, while not systemic (i.e., it does not move through the plant’s vascular system like, for example, Merit does), is absorbed by the plant’s leaves and will move from the tops of the leaves to the bottoms where the mites feed." A lot of the more mainstream systemic products use Imidacloprid, and while they don't claim to work against mites, they also don't mention that one reason that spider mites become a problem is insecticides [such as Imidacloprid] that kill their natural predators.