I have been using hero100's for a while and have not had any problems. However, I put brown ink in the pen and though it writes fine, I noticed when I go pack to the pen (the next day) there is some gunk/crud at the tip of the nib that wasn't there when I finished. It is as if during the night that the pen coughed it up.

Is it the ink that is causing it? It is a leveger ink (cocoa) and I have usually had no problems with levenger ink. I am wondering if it is because it is brown ink (which I normally don't use) that is causing the problem.

Any thoughts?

Hi Sparky!
I think it's the ink,I've noticed the same with Pelikan Brillant Brown,it's a kind of soft sediment,so don't worry about it,
regards,
René.

I would not use this ink in an easily-stained pen, but in a Hero 100 it should be fine. To get such a rich colour, they have to put too much dye in the ink. You're seeing the result. If the ink looks good in the bottle, and the pen continues to write properly, go ahead. You can wipe the crud off if you want, though there might just be more tomorrow.

does it look rounded - almost like tiny bubbles but filled in?

If so - it's likely a yeast.

If it's just gritty stuff - probably just dye particles.