stopping ink-flow and white debris,why?

Hi all,
first time I saw this:I wrote with an Italian pen for some time now using Pelikan green ink.
After some weeks the ink-flow stopped,I rinsed it repeatedly with cold tap-water,no change.
Then I observed white debris (or lime) under the nib.Any explanation?Could it be the ink being not suitable and reacting with the ebonite filling system or lime in tap-water?
I rinsed it again yesterday,this time with destilled water and left it in the water overnight,then filled it with green MB ink today instead of the Pelikan ink,at the moment it works again.

opinions appreciated,
Lutz