Wow, i've never seen that before. Unfortunately, since both the ink and the colours are waterbased, whatever you used to clean the ink would probably damage the paint as well, so it might be a better idea to soak the thing in windex (dilute it half/half with water) to try to get as much of the paint off as you can, then repaint
I have NEVER seen this before. Did you just splash the wash everywhere? Even if you did, it's really weird that it would produce a pattern like that...
Either way, try to localize your wash next time. These warhammer tanks do not have that many panel divisions, so try to use a very very small brush, or a microbrush if you can get a hold of one, then just apply the wash to the recessed details, to areas that are between panels, or corners. The broad open flat areas you can just leave bare.
Also, overthinning the ink won't produce this. It just means that when dry, it will be fainter. BUT, what you want to make sure is to mix the wash VERY WELL, and not splosh it on everywhere, as the water will carry the ink all over the place, just as it apparently did with yours, cuz those marks look like coloured water spots.
Remember, try to kee the wash localized. FOr these tanks it works a little differently. However, you CAN do an overall wash, then repant all the flat areas, and that way you'll have a nice, deep shadowing effect in the recesses.
It's up to you how much work you want to put into it now. I think cleaning and repanting will be a pain in the ass. Just deepen the wash in recesses as I said, then brush over the flat areas to bring out the details.