Kevy, if he is still alive do a FW dip now. Fish likely die from asphyxiation. FW dips can be like CPR. If you can clear the gills and provide good water flow, he may pull through. Get rid of the rock for now and dip him for up to 5 mins in temp matched FW. I don't bother adjusting pH but some do (I think powder based pH adjusters bother the fish similar to too freshly made SW). If he does better with the FW dip, repeat it if he starts breathing hard again. At that point, you can also consider a bath with 5mL Rid-Ich per gallon of water. If you use the rid-ich bath (see link in post 34 above) aerate for 45 minutes or longer with an airstone before using. I use 2 gallons in a 5 gallon bucket. Keep the fish in RI bath for 30-45 minutes if the fish is tolerating it.
Excellent advice!