no flowers on green beans

[jd-11]

I am trying to grow Kentucky wonder beans in a dwc system. they have been in water since about may 25, I have changed the water every 7-10 days with 6.0-6.5 ph. I have an oscilating fan on them. I have leaves that are about 5 inches and vines that are close to 3ft or more. I have cut them back once and went to a bloom mixture with no change. using general hydro nuitreints. They are in the window using southern facing sunlight. any advise would be appreciated.