I'm growing cucumbers in containers in a greenhouse. The plants have a bunch of male and female flowers. I hand pollinate via small paintbrush. The baby cucumbers just turn yellow and die. What am I missing here? Any insight is appreciated.

Details:

-SoCal

-5gal. containers with organic soil in greenhouse with 30% shade cloth over the green house

-I water twice a day. Once in the morning and once in the evening.

-I applied some Dr. Earth fertilizer 3 weeks ago and also have used some worm castings tea every couple weeks.