Direct quotations and quoting 'questions'
No

I don't see a strong case for plagarism here. According to Google:


  [Plagarism is] the practice of taking someone else's work or ideas and passing them off as one's own.


It doesn't sound like you've tried to do this if: despite not being in quotation marks, the quotes were clearly indicated as the work of others. Furthermore you've corrected your mistake which shows good willing. I'd rest easy and wouldn't lose sleep over the matter.