Just lost it all - try again!!
There are several types of calabrese broccoli these days. Some concentrate on 1 big head at the top. Others have a smaller head, followed by side-shoots. Others are almost entirely side-shoots. The type I prefer.
Certainly there should be no yellowing, or sign of being hell-bent on going to seed. Pick anything that looks odd & water well if you can. We had a new type this year which started producing at 3" high!! Had to be ditched, eventually.
Don't expect side-shoots heavier than sprouting broccoli. = Tim