Purchased my fourth pen recently (Charles-Hubert Paris?
Black Lacquer with Chrome trim, via ebay). Didn't get a
converter with it, and therefore I'm using a box of
Mont Blanc (black) ink cartridges that I ordered with
my first pen. The other pens in this very young collection
are using converters all filled with Noodler's.

Now, keep in mind I *just* installed the cartridge like
ten minutes ago, but when writing with this, I'm noticing
a weird behavior I've not seen in any of the pens. Lines
start out very washed out, and then reach normal opacity
mid stroke. This isn't the unusual part. Before it settles
down, I see the color flowing up the stroke, as if I've just
run my finger through a small muddy puddle displacing some
of the mud.

Is this unusual? Maybe the pen nib/feed is dirty?