Yellowing cabbage seedlings

As the title says, my cabbage seedlings have got yellowing leaves. They were started off in the cold greenhouse a few weeks ago and have about 3-4 true leaves each. They were potted on into individual cells a couple of weeks ago and apart from the yellowing leaves are growing well. I have sprouts and kale too and they are both fine.

About 4 days ago I started bringing them outside all day and putting them back in again at night with a view to planting them out this weekend.

Any ideas? I can get a pic if needed.

Also, it's still a bit nippy, are they totally hardy? (Obviously I will make sure they're hardened off properly).

Thanks.

Thanks for that. What would you feed them with? At the moment I only have Miracle Gro 

As the title says, my cabbage seedlings have got yellowing leaves. They were started off in the cold greenhouse a few weeks ago and have about 3-4 true leaves each. They were potted on into individual cells a couple of weeks ago and apart from the yellowing leaves are growing well. I have sprouts and kale too and they are both fine.

About 4 days ago I started bringing them outside all day and putting them back in again at night with a view to planting them out this weekend.

Any ideas? I can get a pic if needed.

Also, it's still a bit nippy, are they totally hardy? (Obviously I will make sure they're hardened off properly).

Thanks.

try misting with maxicrop (calcified seaweed).it's a great tonic for all seedlings but dont exceed the dosage rates on the bottle.good luck.bob