Thanks, Alexandra. I think my pots of rosemary suffered from both over and under watering. I tried to grow it in a greenhouse window with a western exposure but I think spider mites were endemic in that window. If I let the pot dry out a little between waterings the mites would take over, if I rinsed the mites off, the plant was always wet.

I had a house cat at the time so I was afraid to use chemicals on my house plants.
But we have since moved and mites don't seem to be a problem here, and we no longer have the cat so I might try again.