For the most part yes. This is what I am thinking. Yes you seeded your tank with the 30% live rock which did help it cycle but then by the sounds of it you starved the nitrifying bacteria on the 30% live rock that needs food "phosphates" to grow. You said you kept your phosphates low right? So more then likely you didn't get much growth of nitrifying bacteria on the dry rock during the cycle. So now that you have added livestock to your tank (the one fish) and you are feeding it you finally have more food (fish poo and fish food) for the bacteria to grow on the rock. So yes, more then likely you are getting the bloom now that your adding livestock and your tank is starting to actually come to life. Once you get a significant amount of nitrifying bacteria on the rest of your rock you should be good to go.
I found this:
http://www.bioconlabs.com/nitribactfacts.html
this is kinda an old write-up and is not what I would consider completely accurate as there has been advancements in this area since this was written but it still gives you an idea of what I am talking about.
I would like to add I wouldn't change much of what you are doing now. Just get the cleaning crew and give it some time.
