The listed time for sponsorship approval at this juncture is 28 days at which point they will send the file to Singapore. Either way I think it's better to send the additional information to Singapore. I sent some on ours via email with attachments, nothing's faster than that but, just an opinion, don't keep dribbling stuff in as it may delay you and don't fret. If you think it's really important by all means send it. If more comes same thing but try to make it once or twice with only big things. Your application should have been as complete as possible when sent, with the exception of course of pregnancy or something unforeseen like that.
When did you send your application? Don't be too alarmed by our timeline btw because we were unusually long for a straight forward application, it can be much better
or worse from time to time :-( but usually better. Good luck and welcome to the forum