Developing an idea can mean associating them. Perhaps your subconscious mind did it naturally, and now maybe it's just a fallow time. I've heard of reading (for writers) as "refilling the tank", also that some professional fiction writers (one in particular, I'm forgetting the name) found out that they could either have the time to write or something to write about because life experience is what filled their tank so to speak.
Sometimes writer's block comes from a contradiction, like you have an idea for a plot and an idea for a main character, but the personality of the main character would mean that the plot never happens. That doesn't sound like what's going on with you, but I'm just throwing that in there.
Finally, I liked Elizabeth's Gilbert's TEDtalk (on YouTube, if you can access it) on the "elusive creative genius" which were traditions of inspiration: the genius of the ancient Romans wasn't something innate to a person but more like a helpful spirit. I don't think that Elizabeth Gilbert is pagan, but she does believe that being able to go a little bit crazy and talk to these creative forces can sometimes help creative minds to get going.
I believe in muses. There's also a bardic ritual to gain divine inspiration known as the Imbas Forosnai, and Christopher Scott Thompson wrote a great book about that which you can get the PDF for like $3 on Lulu.
Or, it could just be a shift in mindset. Sometimes, I don't feel like writing or reading because I get (figuratively) bothered by a visual muse, or an auditory muse, or even a culinary muse. The text muses take a break. It's miserable when none of any kind of muses are bothering me, but that happens too, and I just have to trust that it happens for a reason and will come back at the right time.
Have you tried just sort of free-writing, to see what comes out? That's another tip that I've heard writers (such as Gail Carson Levine) use to clear the creative cobwebs.