Its really hard to diagnose fish without being able to see them. There are many Malawi fish that will not do well at higher temps. If the fish have not improved then you might consider treating. But unless you know exactly what you are treating, you can't pick the correct medicine? Treating with the wrong meds can be worse then not treating at all. Is it a parasite or a fungus? both require different medications, and not all fish, like loaches that have no scales, can take these meds.
I really wish I could be of more help, but I don't even know what kind of fish you have in the tank, I would only be guessing.
You might try leaving a message over in the hospital section at www.Cichlid-forum.com
Fill out their form and I am hoping they can help you.