Anniejolly, there have been two VERY HOT spells here in the Bay Area recently. I monitor my Bernese Mountain Dogs for heat stress very carefully, but we were already committed to outdoor events on May 15 and 16 in Vallejo, so I know that it was over 100 deg. F on those two days in Vallejo, and over 90 deg. F in El Cerrito (I watered both morning and evening both days due to complete dryness of veg's). Maybe Greenbrae was also very hot then?
And then, last week, maybe the 18th through the afternoon of the 22nd it was very hot again. San Francisco set a record maximum temp on Thursday or Friday and it was 89 deg at 11:30 at night here in El Cerrito one evening. The fog returned Sunday afternoon (gracias a Dios) and now we're back into our usual pattern.
Your tomatoes might have gone into defensive mode, given these heat spells. Check to see whether their soil is dry, damp, or wet, too. Maybe liquid kelp will help them feel better, if the soil is dry or barely damp.
USDA Zone 9/Sunset Zone 17