One of mine has done the same if you are in the UK? could it be too much water this wet spring?

Are you feeding them and if so with what?

Are they in full sun, or shade?

Whats on my mind is; You are feeding them with possibly a high nitrogen fertiliser and you are getting foliage at the expense of flowers.

My other thought is 'poor light' this can make them 'draw'!

Then there is the other thing and that is; they are not due to flower yet, I am finding that this year is about three weeks behind last year!

many thanks i feed them bonemeal
regards rain.

Bonemeal is high in phosphates and is a very slow release fertiliser, and need only be applied once per season!

Phospates are generaly associated with root growth so you might be better giving them a high potash feed to encourage flowering.

Use a liqid feed such as any tomato food as opposed to a granular feed and this will act faster!

I also found that helpful Teegee thanks