Checking my diary it doesn't say
They require a long growing season I sow mine end of April.
Last year it was 18th April, took 5 days to germinate pricked out on 27th April and planted out 29th May. Were ready in October/November.
will they grow any more or shall I just pull them up
No! I would treat them a a 'leafy' veg and just pick the more succulents leaves near the centre and get them in the pot!
What I can't understand is; why they haven't hearted what variety were they? I have found 'Wintessa' reliable see here;
http://tinyurl.com/3xpxjpI think you might have to invest in some bird netting! and if you do get good quality nets it pays in the long run I have had mine for many years.