Jelavic has scored once since December 1st and Fellaini only has two goals in the same period.
Looking at the sequence of results:
Up to December WWLDWWDDDDWLDD (5 wins out of 14. 22 points out of 42= 52%)
Since December DWDWWLWDDWDLL (5 wins out of 13. 20 points out of 39= 51%)
we've actually been pretty consistent this season. Arsenal, Spurs and Liverpool all took some time to get into their stride. So, while we've been treading water since day one, they've made up ground and it's given the impression that our results have been slipping.
Also, we were creating lots of chances without finishing them in the early part of the season.
Goals up to December: 24 (1.7 per match)
Goals since December: 17 (1.3 per match)
Goals conceded up to December: 18 (1.3 per match)
Goals conceded since December: 16 (1.2 per match)
Up until December our biggest games were United (h), Liverpool (h) and Arsenal (h).
Since then we've played City (a), Spurs (h), Chelsea (h), United (a)
Looking at the table it feels like our season is falling apart but we're performing only marginally worse than we were earlier in the season in terms of results, our games have been more difficult and some opposition teams have started to find form.
There are things that we can improve on though.
Fellaini is getting manhandled at every opportunity and the refs seem to be letting it go, so he's not as much of an aerial threat from set pieces. Rather than having him standing in a pack (where it's hard for the ref to make out infringements) and hoping that he can bundle things over the line from a standing start I'd get him to start further out and to make sure that he runs and jumps for the ball. It would make it harder for defenders to grapple him and it could prove a good distraction to allow other players in.
We need different attacking permutations. Mirallas, Naismith and Pienaar could all offer us something different playing in the hole. Teams will spend all week working out how to shut down Fellaini and the Baines- Pienaar combo, so we need to mess with them and cause them problems. It's not enough just to interchange Mirallas and Pienaar during a game. And, with Anichebe out injured, Vellios should have made it on to the bench today. How much worse could he have done recently than our misfiring forwards? Jelavic, Fellaini and Anichebe have contributed 6 goals between them in the last 12 league games. It's far from Champions League standards.