Are most of your hubs idle? I look at your profile and see only 2 hubs but in the side it says you have 30 hubs... also the hubs you've featured in the sliding picture bit aren't listed underneath as hubs, which makes me think many of your hubs have been idled or are no longer featured...
This could explain why your traffic has dropped as these hubs may no longer be indexed by Google.
If you are looking for more viewers you need to learn to do keyword research to target specific people looking for something. Ask yourself, "who wants to read this and what will they type into Google to find it?" How many people are also looking for that exact phrase or keywords? Is there enough traffic or is it too competitive?
People tend to Google things they are interested in or for the solution to a problem they have. How do your hubs fit into this?
These are things I have noticed with popular hubs and articles on the internet. It doesn't matter how well something is written if it's something that very few people are interested in or there are millions of pages on that same subject already.