Go with the bleach mixture, on one of the hardshells. If necessary, try a stronger mix. You have nothing to lose, cause they are all functionally useless if you don't get that crap out.

Seven hardshell cases is a bit of a blow, but obviously they did not have the instruments in them...did you see the ad for the Lloyd Loar F-5 mando that was in a flood and all the seams opened up? Ouch...

I reckon if the plush doesn't make it back to normal (and I suspect it won't) you could just remove it and put in 1/2 inch packing foam...works just as well.

Good luck...
W-O