Its not bad thing,seed company's will say certain genetics will be done in 7 week or 8 week i all ways add a extra 12/14 days ontop of this because i never chop untill the plants are crowned of perfect.
Its there way of getting you to buy a plant thinking it will be done in a set ammount of time this very rarely happens to many factors play a part,this to me says that the temps in the room have been pretty good and the other parts of the room are ok they normaly finish early if the room is in perfect condition,but a finished plant to them is not a finished plant to me i like them to be at a certain point before i lop them down.
they will look done early if the nutes you are feeding is too strong for them,let them run for has long has they need rather than rush them along.The last two week are the most important part of flowering so don't rush them