Dig them up. Check the roots. Let us know what you find.

Hi, welcome to GoY, first of all, what is your question ?, personally I don't grow veg, but I do know that cauliflower can be a bit temperamental, and sometimes difficult to grow successfully, hopefully someone will be able to give you some advice, we have a lot of veg growers on here, Derek.

I think maybe you are growing them too close together, caulis like to be in very hard ground, as Scrumpygrat says check the roots for club root, in this hot weather make sure they are watered well and try to keep the curds covered by bending a couple of leaves over them, also as Derek says caulis are very difficult to grow, I put a small number in my allotment and sometimes they do well and another time they just shoot up and go green, another thing I can suggest is to try different varieties as some can do better than others, it is just a case of trial and error until you can find one that will grow in your plot.

Also the treatment at the seedling stage is important. If the baby plants receive a check at that stage they will not make decent curds later.
Temperamental things. I once grew some on my allotment with TLC . Failure. Next door planted some and due to some family stuff then neglected the plot. The caulis were overgrown with rank grass and made fantastic curds. There's no justice.

Thankyou very helpful