I think the problem may be associated with your temperature, that temperature is acceptable for CRS but it's too cold for them to breed, they breed around 70-74 I think.
IMO SF tap water is just a bit too alkaline for CRS. I haven't tested TDS, but I wouldn't be surprised considering SF tap is in fact from Hetch Hechy. I was able to breed a nice amount of CRS only topping with tap (aquaplus for the chlorine) a couple months ago.
Everything, Nothing, Nothing, Everything