One of these plants is not like the others

Sorry for horrible pic quality but the camera was free

first 2 plants are 2 diff strains i bought off the internet, the third is bagseed from at least 5 years ago. Planted them all 5 weeks ago, same nutes lights everything.

Anyone care to guess what strain the midget one is? It might just end up being crap, but I doubt I woulda saved seeds from bad pot. I know I've heard of some strains that grow retardedly small but don't know any names.

Not sure, but the midget is gonna have one helluva nice main cola and you should train it that way. Lop off any side shoots and concentrate the energy straight up the main stalk.