Yes, you can wash your designer cushions, no problem at all. 3Beaches fabrics are made in Sunbrella so simply follow the machine washing instructions.
Details can be found here (link).
In regards to Mokum, James Dunlop and Catherine Martin, they recommend a warm wash, do not dry clean, tumble dry and DO NOT directly iron these covers once clean (use a barrier cloth) as some fabrics will melt under intense heat as they are olefin based.
