Not being a startup in these cases is a good thing.
A single LLC is completely sufficient for your purposes. If and when you take on a partner in one of these apps in hopes of building a company around it you can form a second LLC to maintain a clean ownership structure and give a place for additional people to vest some shares over time.
Just for the record:
I don't think I used the terms "app" and "startup" interchangeably, I was specifically trying to distinguish "profitable business" from "webapp".
Also, we've all got our pet definitions of words, and HN does around words like "startup" in particular, but HN mythology notwithstanding, any new business is by definition "starting up". Even under the "compress your working life into four years" notion that is popularly tied to the word "startup" here, I'm not sure how "single founder" implies "not a startup."
Hope that doesn't come out wrong. I sincerely appreciate your feedback.