it is also very young. young plants will show things like that b/c of genetic defects. yes it could be a number of other things. but if you start making adjustments and going ape shit about the very small brown tip right now, then you could just as easily mess it up worse. in general, that plant looks good. chill out, smoke a bowl, and let it get growing a bit first. if it gets noticeably worse in the next week or so then let us know. it's really just too young to make any diagnoses at this point and there are too many variables, unless you were growing in a COMPLETELY controlled environment, which you aren't.