Yike. Check the fertilizer package and see if it was the "weed and feed" type. If it was, it contains a broad-leaf herbicide, meaning the poor cactus is probably doomed. If the fertilizer was just too strong, then perhaps you can either replace the medium or flush it out with distilled water. If any green parts are left, maybe you can cut them off and re-root. Are you sure you want to marry this guy?

LOL, Itecato..
After he sprayed your Rick-Rack, did he tell you or did you find out later?
Did he spray the leaves, soil or both?
After you discovered your RR was hit w/outdoor fertilizer, the leaves should have been hosed thoroughly, wiped, and rehosed..if soil was hit, you should have leached until water flowed from the pots drainage holes..

On the other hand, if you recenlty brought your RR outdoors, it could be too much light..Did you acclimate the plant when you first brought out? Was it sitting in full sun, or in a shady spot?
Sunburn leaves turn red or brown..crispy brown, but root burn caused by excessive fertilizer also causes brown foliage.
Hopefully you can save your plant..I'd set in a semi-shady spot for a while, gradually adding more light. Remove damanged leaves. Good luck, Toni