Burned Bottom on Baguettes

Hello - I baked baguettes on a 'well seasoned' metal baguette tray that appeared to be used very heavily in the past: holes were clogged and the metal was blackened.  I baked over a stone, but because of the design of the tray, there was air space between the stone and the tray.  

Is the blackening of the tray the cause for the burnt baguettes?  Would a tray that is newer and brighter make a difference?  Should I forgo the use of a tray altogether and bake directly on a stone following proofing using a couche?

Thank you!