Hi fellas, recently got my house rendered and also a wall on my outbuilding, the house looks oerfect but the wall on the outbuilding has got streak like stains down already, i think its due to the rain dripping down off the roof as there isnt any overhang on the felt. Any suggestions how i can clean it off and also prevent then coming back? Can i power wash it off on a gentle power? The rendering was only done 4 days ago