CFB yellowing leaves

I think mine are too bedraggled to show a picture. They were originally sown in the early days of March when we had that lovely weather during the beginning of lockdown. Far too early, as they were very leggy and straggly when finally planted out. They may just have reached their allotted life span. Nonetheless they will be sown again next season. I have also grown merchant of venice which is very similar but yellow. The two are very pretty together in a stir fry.