Inks within the same brand/line does differ in performance dependent on which colors you pick. Not sure about the Edelstein since the retail price for them in my country put me off getting them, but I've used the 4001 series in a few pens and never had problems with them, except for flex use. Edelstein is supposed to be wetter flowing than the 4001 series from what I've read on the internet; and have decent performance throughout.
There are many inks on the market that are not really pH neutral, but are still used regularly without any issues. Noodler's ink are mostly not dangerous to use by themselves; bsb seems to be just a rather extreme case. The situation that usually causes problems is when there is residual ink of another brand left unflushed in the pen, and noodler's is thrown into the mix, and they react (fyi, this applies to most inks as well; I've had slight staining from mixing pilot blue black and waterman serenity blue, which had to be scrubbed heavily before it came out, and severe staining from mixing waterman serenity blue and pelikan 4001 brilliant red that I still haven't been able to get out of one of my demos.) Just don't mix noodler's another ink, or even another noodler's unless its specifically stated to be a mixing ink like shah's rose, navajo turquoise etc.
And by the way, I've had pens that I ran over 200 ml of water through the feed using a large syringe, saw that the water was extremely clear, and then removed the nib and feed to still find some ink left behind. So there's always the chance that your pens aren't always as cleanly flushed as you thought.
@genkidama - imo it doesn't sound like an ink problem. despite pilot's overall good qc, I have had several pens from them refusing to write/have hard start problems like yours. The tines were too tight together on one, and I had baby bottoms on another. The first was fixed by flossing and spreading the tines with a brass shim, the second, I reground. Try the brass shims first and see if the problem goes away.
just curious, lefty underwriter or overwriter? if you're an underwriter, you don't really need a fast drying ink. Otherwise, there's a few inks you could look at - Noodler's Bernanke Blue (fast dry), Sailor Sei-Boku (nano particle ink, blue-black, very fast to dry too). I'm lefthanded, write under the line, and use japanese ef and f nibs on a daily basis without issue.
