"ils broient du noir"- i think this could translate into english as "they are ground down" but i'm not sure. also, is this an informal phrase? thanks in advance 
Yes, it is an excellent alternative to what's been suggested, note also that 'in the doldrums' is often used to describe an ailing economy ('une économie en crise/dépression économique').Jean-Michel Carrère said:how about : be in the doldrums ?