Might be due to weather. Here, I see a lot of growth happening when the temps are at 90 degrees. Also, so plants will bolt sooner, but depends on the strain.

This happened BEFORE the heat wave we have just had.....

It's the nature of the beast. It doesn't have to be a heatwave - just warm weather - to bring it on. It's a very short-lived annual which can live out its entire life in a few weeks. Not unlike coriander, in that respect.

In my area we have had very dry conditions for this time of year. My spinach bolted before getting more than a couple of inches tall and before the week of 90 degree heat. Being on well water rather than public water, I am limited in how much water I can throw at the garden so I'm not entirely surprised about the spinach. I guess I'll have to try for a fall spinach crop.

Perhaps dryness/lack of rain may be an issue for you as well if you don't think heat is the cause.

FataMorgana

if some of my herbs have gone to seed is it too late for them. Do I need fresh plants for this season?

You have to tell us which "herbs" if you want any useful information. Not all "herbs" are the same!

FataMorgana

Did you fertilize? Apparently herbs don't need or want any of it. I gave my herb garden some and literally overnight the dill and basil all had seed pods.

Not all "herbs" are the same but many culinary herbs do prefer lean soils.

FataMorgana