I asked a question yesterday. I was trying to be as specific as possible but today I found out that the question I was asking was incomplete.
Is it a good idea to change the title of my question?
Absolute. Edit your question title or copy at any time. If you are adding additional information to your question it's good to note that clearly this a header named "ADDITIONAL INFO" or "UPDATE" or whatever you'd like to use...
After reading your particular question a bit more, I have one suggestion to make for anyone else who has this issue:
If the answers got you part of the way, but now you have run into a highly-related problem (as you did), it's better to just update the question (as you did).
However, if the answers helped solve that issue, and now you have run into a separate problem, it's better to ask a new question. The reason being that if you change the original question significantly, all the existing answers become invalid and turns the site into a mess.
The difference to ask yourself is: if someone else stumbles across this thread with the same question, is it likely they will also have problem you have now? Just remember, the goal of Stack Exchange is to build a useful database of questions and their answers for future visitors (not just a site full of one-off discussions), so we generally encourage anything which helps further that goal.