Ink? Why not? Go for it, if it works for your image - which I think it does.
Some watercolor societies are purists and disallow ANYTHING except transparent watercolor.
Some, like the Ohio Watercolor Society allow anything including collaged parts, glued on textures, gouache, acrylic, etc.
Here's what I think. Make your art the way it suits your art. You're good. There will be recognition of this. Forget the people who dismiss it because you used a bit of ink. Pffft!
One thing I really would consider changing is that green, though. It's acidic and too intense for the rest of the painting. You simply don't need it that bright. What od you think about glazing over it in a warmish neutral? Soft orange, perhaps?
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