Unplug your heaters, and check your temps in a day or so, if its drop to around the ambient temp you know its the heaters that are providing the additional heat.
At the moment there's no need to have your heater on, your tanks will be hot enough without one, so just unplug it until it starts to get cooler again.
If your worried about your fish increase your surface agitation so the water can carry more oxygen - the hotter the temp the less oxygen the water can hold.
As for the water in your tank being warmer than the ambient temp - water holds heat a lot better than air does, so it takes longer for water to cool than it does the air.