Diamox isn't a magic fix. It only helps alleviate the symptoms. The temperature needs to be turned down, the parameters need to be perfect, changes may need to be made to setup and/or husbandry... so far, you haven't given us any information about your seahorses or your setup.
What is the temperature, pH, ammonia, nitrite, nitrate, salinity? Where did you get the seahorses, where did they come from (CB, WC, or TR?), what species are they, how long have you had them?
Move your seahorse to a barebottom hospital tank and drop the temperature to 68*, and then try to give us more information about what is going on. Diamox can be purchased through Inhouse Drugstore.