this is fairly common with a well insulated spa during the hot/humid summer months and it usually requires you to start with a lower set temp than normal and to dial down the length of your filter cycles during those months (some spas even have a "summer mode" built in to the controller)...when pumps run they create heat, that heat + the combination of 90+ degree temps and humidity will "overheat" the spa. Now I'm not sure why you added cold water and it didn't return to "normal operation" like you said it could have created so much heat that is "fried" a component, of course your tech will determine that tomorrow...good luck