This occurs from time to time and is not something to be worried about, it is not a disease or a deficiency of any sort, just a weird genetic quirk of this particular seedling. I have seen all sorts of weird growth patterns and none effect potency or plant health. Things exactly like this, going from 1 into 3 tips, nodes without branches, nodes with only one branch, nodes with no branches but with 3 or 4 leaves, plants that "self top" - the list is endless.
Hope this helps,..........
Organoman.