Sounds like way over-fertilization. Especially with nitrogen. Root crops don't need and don't tolerate lots of nitrogen. It results in lots of tops but little to no root development. Stop fertilizing and see if they can adjust but it will take time. Or you can just replant.

Dave

Agreed about nitrogen. Enjoy your beet greens. That's what you're growing.

Thanks, so if I was to start again. Would you fertilize at all? and if so with what?

Potassium/phosphates (and to some extent boron/borates) is what is really needed for root crops, but you'd be smart to get your soil analyzed before you put any on. If you've amended well with compost, I find it hard to believe that any fertilization is really needed. I never do, and have excellent crops. If you feel you must add nitrogen, do it early, and not later.

Agree with the above. Given all you have already added the odds are nothing is needed but the only way to know for sure is to get a soil test if available for a reasonable cost.

Dave