Raising temp is a myth that comes from freshwater ich which is a completely different creature.
The tough thing about diagnosing SW rich is that anything that causes a skin irritation will lead to small white bumps appearing on the fish.
I generally prefer the "do less and if they are eating they'll fight it" approach. However with rich and ich-like parasites other are some exceptions.
If they are breathing hard and flashing (rubbing on rocks) their gills are being damaged which could kill them without ever showing an external spot. Think Pneumonia.
Also particularly with scaleless thin skinned species by constantly shedding slime and bits of skin the process of osmoregulation (keeping their body fluid levels balanced with the outside sea water) becomes more and more energy intensive. Their appetites may increase but eventually they will not be able to take in enough calories to maintain cellular homeostasis and they will begin to waste away.
Moving them into a tank where you can lower the salinity will relieve stress from the fish and increase the stress on the invertebrate parasites immediately. Even if you don't do the full hypo QT, some time in lower salinity can tip the balance and allow the fish to recover while putting severe stress on the ich.
Plus....Chances are when you have them out anyway...you'll do the full QT anyway...