Kymmie's is quite right, a minor temp change of a few degrees is not a problem for most fish species. Some such as the rarer gourami (Chocolates, etc) could have problems; but the fish you mentioned are accustomed to this in their natural habitats.
The heavy rains that fall in tropical forests always cool the water by a few degrees, and this can stimulate egglaying fish into spawning. Their instinct tells them to spawn at the start of the rainy season, so if you do a water change with slightly cooler water, and do it on an overcast day (low pressure system), it will initiate spawning with many tropical forest fish like characins, corydoras, etc.
I also deliberately reduce the temp a degree or two in my Amazonian tanks; never in the Asian tank though because of the gourami.