This is the first time it’s happenened:
I overwatered the tomato seedlings and one hasn’t survived. Fortunately, a new one has popped up and it is is from a packet which has lots of seeds (in comparison with the organic tomato seeds).
On the other hand, as can also be seen in the above photo, the echinacea have survived the winter, producing what seem to be strong new leaves. Perhaps they would have been okay outside but I’m glad I didn’t chance it.