Hermit was a source of bleeders but he is well back now.
This from Byron Rogers
"EIPH is a progressive affliction in that all horses, to a certain extent, bleed. Basically it starts at the back of the lungs and move progressively forward. For some horses it gets to a point and doesn't go further, for others it progresses to the point of nasal discharge. What makes one horse discharge and another not, is quite complex and involves both genetic and environmental factors, training intensity/frequency, surface, drugs, and the specific structures of the equine respiratory system."
"...Northern Dancer was a bleeder, but it doesn't seem like he sired a lot of bleeders"