1 plant of 7?

i havent got pics atm but i can try and describe it, this is my first grow so im a little inexperienced. basically 1 of my 7 plants looks like its finished but the other 7 dont and im only in like 5 weeks flowering i think. the leaves are going yellow/brown only on one of them. but the other 6 are fine and still growing. the plant thats got the ?problem? was one that i topped out when it was young just to see what happens. so yeah any ideas?

indoor? outdoor? grow medium? a lot of un answered questions. pics sure would be helpful. but it could be something with the pH or nute lockout