Waterproof ink?

I've been using DeAtramentis Document ink for years, and it was always waterproof. But I got a new bottle of Urban Grey recently and when I applied watercolour on top of a fountain pen drawing I did with it, it became a grey mess with no definition. So when I got home, I did some testing, leaving it to dry for longer, but still the same problem. I thought it might have been my fountain pen, which I had recently cleaned. But no, I tried with a nib pen, and a brush. And it still bleeds.

So I checked their website, and they no longer say that the Document ink is waterproof. The Artist ink is. And lightfast. Maybe I should shake the bottle first and see if it makes a difference? I did buy a few colours of the Document ink that time, to amortise the shipping, so I'm going to have to test the various colours I got! Disappointing. But First world problem, I guess!