I don't experience spring sickness where I live, so the affliction in my own seedlings is not something I can address. I have received plants from the north that exhibited it, and they were moved out.
I am one who believes that plant habit is just as, if not more important than, a pretty face and in saying that, my line of thinking is ...why keep any seedling that you know is going to suffer from spring sickness? Yes, they very well may grow out of it, but if you have siblings that are NOT affected by spring sickness, why keep any that do?
In my garden, they would be culled immediately.
