Hey sorry about the little plant but I agree with the rest....there are multiple things that can and will stunt a young plant.... And then.... Sometimes they just don't want to grow.... Which is what happened to me recently. All plants started at same time... The now extremely stunted one is the one I believed that was going to take off due to how fast it started growing.... Well fast forward to today....it hasn't grown anymore in the last 30 days where as the others have taken off.
Photos : group photo of all plants the same age.
And a close up of the 48+ day and old runt