Seedling leaves… ongoing

[Johnny Phantom]

Hello Charles,

Thanks for all the advice – including the details on the other threads, including ‘Steps to victory’!
Our problem with the brassicas is apparently ongoing. We’re on our second sowing of cabbages and cauliflower, and the first sowing of brussels sprouts. As you know, we were trying the fibre compost, and we swtiched over to West Riding seed compost.
After the description of our last efforts, we followed your tips and advice, but we’ve run into the same problem – the brassica seedlings start off looking really good, and we pricked them out and moved them into individual modules just before the first true leaves start appearing. But then, after perhaps a week or so, the seed leaves start turning pale, then start drooping, and then the whole seedling collapses.
We’ve wondered whether it’s the compost (then we changed from fibre to the WR seed compost); we’ve wondered whether it’s tap water (which we then switched to rain water collected in a water butt); we’ve wondered whether it’s the seed (we’ve used Tamar Organics and Chase Garden organics – the Tamar all come up well, but all die off; the Chase Garden are still with us… just); we’ve wondered whether it’s air circulation or ventilation in the conservatory; we’ve wondered whether it’s temperature or sunlight (we moved them outside into a small covered cold frame a couple of days after pricking them out, on sunny days – we discovered today how hot the cold frame was getting inside); we’ve run out of ideas!
The seedlings all seem fine, and a nice healthy, dark green, with firm seed leaves. Then we pricked them out, a few days passed, and then they began looking pale again, and began drooping and dying off – as they did the first time.
Any ideas? We don’t seem to be able to get these right!

Thanks in advance…

JP and JP’s wife