Excellent. Thank you for the reply. I'll convert the flow to onRequest, instead of onReceive, and poll Slave 1 from the Master. Did I get that correct?
Interestingly, the serial printLn's that are part of the receiveEvent on Slave 2 does not seem to mind them.. those Tx & Rx OK. I added them just to debug... but from what you're saying it seems like I'm creating a fail-state. Please help me understand why they work in one instance and not the other.
Also, do calls to different slave devices take any processing cycles away from the non-called slaves? My goal is to keep Slave 1 doing it's work as quickly as possible, and not "distracted" by other communications or processes, which is the whole reason I went from 1 to multiple Arduinos.
The delays were just more grasping at straws.. I'll pull them. 
Is there a case when delays are critical when starting up communications? I see them suggested for the LCD and others..They seem like band-aids for many peoples sketches. I'm having a difficult time understanding the distinctions when it's truly needed.
cheers, and thanks again. I look forward to posting again when I've made the mods!!!