Brussel Sprouts not firmed up

by Maureen
(South Yorkshire)

I set seeds of 'Evesham Special' sprouts on 11 Mar this year and subsequently pricked out into 3" individual pots and when fully established in pots planted out into a raised bed on the allotment, firstly firming down the bed.

They are now 3 foot high and have formed many sprouts but they are all blown. The plants look really healthy and very sturdy having been staked early on.

On testing the ph of the soil it registers around 6.5 to 7 and I only use chicken manure or blood fish and bone for fetilizer.

I also planted a second sowing of 'Green Marble' sprouts, a fdew weeks later, which are almost as high as above and in the same bed and they seem to be forming firm tight sprouts.

Any idea why the Evesham Special have not performed?