Digital BW, The Print

I just purged my old piezography inks and reinstalled my CIS with MIS 
inks (with new cartridges) and now am getting NOTHING out of the 
magenta nozzle. Yes, I had perfect nozzle check before I did it. I must 
have air in that one hose. My question is: I'm pretty sure I have to 
repurge the CIS and do it all over again - but do I have to get new 
cartridges, since I'll be putting in the same ink that's in them?

If anyone has other suggestions, I'll try them.

Thanks,
Barbara White
http://www.barbarawhitephoto.com