It isn't difficult to destroy a DC fan motor by spinning it too fast -- which is likely what happened.  Even on a low setting, the blower likely spun the fans far too fast. Before you look at downgrading the firmware, replace the fans in question.  
Hello all, Well, I think I just added some stress to myself. I updated my M17x R3 from the A08 bios to A12, laptop started fine, repasted cpu and gpu with new thermal paste, and then (and I think this is where I went sideways I hope) blew out the fans, not with compressed air, but and this is cringeworthy, a leaf blower I had (on low setting).  Now I don’t have cpu or gpu fans, and I am not sure if it is because of what I did, or the bios? I’d love some insight, and hopefully not much scolding.
M17x R3, CPU/GPU fan issue