He started the season centering Forsberg and Granlund, it was working very well until Forsberg got hurt. After that Duchene was moved to RW with Turris and Granlund. I think they should have simply pushed Turris into Forsberg's LW spot because Granlund is useless there and Duchene is more limited in a wing position.
He was also injured for a game and may not have been totally healthy since coming back, but nobody knows. I wouldn't worry about his production until he's had another 3-4 games with his line intact, which it looks like it might not be since Forsberg was back with Johansen and Arvidsson by the end of the last game.
Either way, it's the whole top-6 that is struggling right now after a hot start. I think his upcoming road trip starting tomorrow will be a good thing for them to regroup and focus on nothing but their game.