No offence, guys, but it sounds to me like you had good runs for a long time and have simply come up against better quality opposition. Certainly that's the case in the CL and Cup, as you tend to find that good, knowledgeable managers are usually in the later stages.

However, that being said, I've noticed a lot more 'missed chances' of late. It may have something to do with the lower scores people are seeing...you still have the same amount of possession/shots/dominance, but score fewer goals, hence lower efficiency stats. To be fair, people were winning 10-0, or better, regularly and that's not very realistic, is it?

But I have also had strikers who started a season on fire and finished it not being able to hit the side of a barn. I usually go on ratings and trust that the goals will return if the performances are good enough. However, that's your decision. You could sell and replace. Either way is a risk.