Easy Tando, not everyone comes in knowing water chemistry and if you're dilligent in your care and water changes, it's entirely possible to go years successfully keeping fish without knowing of the intricacies of pH in an aquarium. Learning through experience, while occasionally messier, is far more effective than simple book learnins'.
However, shedge, if you are serious about fishkeeping, it's time to invest in a test kit. You can get the Hagen/Nutrafin mini master test kit for about $30. It contains all the tests you need for fishkeeping and a bit of info on the significance of each. Take it with a grain of salt though, each tank is different and the info they provide is very basic.
That said, Wippit and Celura have covered two important diagnostics you should check and include in your posts for help. Water parameters, age, appearance, habit, etc. are all important diagnostics.
Celura's right about the heater, I think if you were serious about heating it, you'd need some form of external circulation to move water through the two tanks and a third reservoir for temperature control. Tricky, doable, but probably more work than you're looking for.
Besides, if your room temp is around 79, your tanks will adjust pretty quickly, they're small.