Clorox & A Garden Hose
I also just cleaned my cushions. I was afraid the 1983 zippers from mt Mac 25 might fail, or I would never get them to look right again, stuffing the foam inside, so I washed the imitation leather bottoms with a mild concentration of Clorox in warm water. That knocked down the mildew. I then hit em hard with a garden hose with a power nozzle. A pressure washer may be better. I really filled these with water. While I washed them, I had someone stomping heavy on them, walking on them. I did this till they looked clean, and clear water came out of them. Let dry (weeks)
The city water has enough chlorine in it to help kill mold and such.
I washed all but one, so I could compare results on a before and after, and the results is amazing.
I need to do that last one.
Note, I did not spend any time trying to Clorox scrub the tops of the cushions, as that may bleach out the colors.