Thanks Gpaw for your input 
, I’m starting to think the same, although it doesn’t look like botrytis, sooty mould or fusarium. Just the hibernate have been affected so maybe the others are more mould resistant.
Temperatures are in a tolerable range:
Humidity raised lately because I stopped the fan thinking it could be windburn 
, there are two small dehu but guess I will have to work on that:
I am thinking about spraying with diluted aspirin and waiting more for the pots to dry 
. Glad we’re finally getting some conclusions … 