Implications of Updating EP Stream Cadence

Hi, 

I have a nurture stream with a cadence of Tuesday morning, every 2 weeks. The first cast was 5/31 to an audience of ~80. Last week 400 additional leads were added to the stream and received their first touch on 6/14. We did not receive approval on the second touch until today, meaning the first group missed their second email in the cadence as it was not activated. If I update the cadence to Wednesday afternoon (so it launches today), will both groups receive the 2nd email or will  the 400 leads be still be held for 2 weeks?

If they it WILL affect both groups, is there a way to manually hold the 400?

Please advise - thank you!