To care for mouldy Nubuck leather, Valmour recommends to proceed in 3 steps :

1-Thoroughly clean the nubuck leather with OMNIDAIM  by using the large Spreading Brush Saphir. Let dry completely. 

2- Take off shine with the Cleaning Sponge Suede Nubuck Saphir.
3- Afterwards, apply  Rénovétine Saphir Spray.