Since you are a fellow SoCal breeder, your whether is pretty much the same as mine give or take a few degrees -- I know your specific area.
I have a room heater that raises the ambient temp to about 83-85 during the day. My night temps drop to about 77-78. Some of my racks have no belly heat during night hours -- and others do.
The ambient temp difference from day to night being 3-5 degrees lower is the important factor -- if there is one. Balls will adapt to what you are doing to breed. I do like to have a COOLER end of the rack for girls to build. I am sure you are doing just fine -- don't stress!!![]()