Have the nights been a little cooler than when they first came up? If so, that might be the reason for growth slowing down. Night temperatures near 60 or below will pretty much stop the growing process until the night time temperature goes back up. Here is some general info on tomato growing for you. I hope this helps.
http://www.tomatodirt.com/toma...
I noticed you list your USDA zone as 10a.... I thought most of San Francisco was considered to be zone 8. Perhaps that may have something to do with the slow down? Possibly you are in one of San Francisco's many micro-climates.
http://sfdpw.org/index.aspx?pa...
http://sanfrancisco.about.com/...
