I was taking pics today of my Helleborus and I found these leaves. I looked up Helleborus disease and could not find it. I know there are helleborus with purple leaves but I did not see this last year. I have tons of Helleborus that are cross pollinating and producing new plants but I don't think this is what is happening.
This looks like a normal reaction to cold. Some plants are more sensitive than others, and even within a species, some varieties are more likely to change color than others. Your seedlings are, of course, just another way of saying different varieties.
