Crystal Lemon Cucs - Flowers but no fruit

[cupcake]

Mine are rubbish too! Not even marble size.

[di]

We're in the non productive gang!
Being confused as to how best to look after them,I've gone for both methods advised....a couple of plants getting watered only when absolutely needed(Chappie at lottie claims they don't do well with too much water)...the others getting lots of TLC...I read the bitter taste comes from too little water.
Difference between the two lots is zilch...not a cucumber on any of them!Starting to have wondering moments about the quality of the seeds...would that be a factor?
A lot of my squash are having similar problems,from the same supplier,lots & lots of male flowers,but no female.I've done absolutely nothing different this year & my pumpkin patch is usually my pride & joy...this year however,from about 20 plants I've only got about ten fruit and a lot of them are on the same plant!!!