Too late to fix IMHO. If you layer on top of that you\'ll lose all detail. Strip and start again, here are my suggestions for the look I think you are going for:
Start from a black undercoat, thin your paints lots till they have the consistency of milk. Start the metallic bits with tin bitz, wash that with brown ink. Then highlight that up with brazen brass then shining gold. Brown ink wash again if you need to restablish the detailing.
For the black, take a mix that is mostly black, with a hint of one brighter colour (I\'d suggest codex grey) then layer it towards the highlights till you have a really thin line of codex grey at the edge. If it all ends up too bright, a really thinned down dark ink wash can darken and bind it.
Other details in whatever colours suit, but I find that red, black and white are always the best heraldry and detailing colours for grey knights.
Hope that helps.