Problem or No?

You don't give any information in your diary about your nutes - how much of what - but losing green usually means it needs more nitrogen - so I would give it a little bit more of your grow nutes. Since this is an auto, you should also be adding some bloom nutes about now to help it as it goes into pre-flower. Autos, in flower, won't need/don't want much nitrogen so when it gets to pre-flower, you can start knocking back the grow nutes which contain the most nitrogen (I cut out ALL grow nutes when mine are in flower relying only on the nitrogen provided by the bloom nutes). Good luck - not a big problem and easily solved... just don't OVERDO the nitrogen as that will cause a lot of problems, too... balance (ugh!)