No, it is not normal, but it does happen from time to time.
Once you have been growing for a while you see all sorts of strange growths, buds on leaves, buds on leaf stems, leafs growing on leafs etc, etc.
It is nothing to be worried about, it is not a disease, deficiency or something you have/have not done.
It will not affect, yields, growth rates or potency, it is just a weird growth.
If you go to week 7 in my diary "cannabis conundrums", I have posted some pictures of various mutations I have seen in the past.
Hope this helps, Organoman.