In my experience, rubber plants don't need very much water at all compared to most houseplants. Some Aloes require less, but yeah. Watering them too much or too often can give them issues. If the roots stay wet on the bottom very long at all, the plant can visibly change fast.
Remember, rubber plants like acidic soil. So, if you gave it any alkaline soil amendments (such as rockdust, ashes, or calcium), that could be a problem. In fact, standard potting soil might even be somewhat too alkaline.
Also, I would advise against giving your plant a foliar spray of calcium nitrate. I gave mine one, and it didn't seem to like it (even if the plant started growing faster afterward; the already-existing leaves looked unhappy). Foliar sprays of ammonium sulfate don't bother mine. It should be noted that some other houseplants seem to love calcium nitrate foliar sprays, though (note that you need googles and a mask when spraying nitrates), such as holiday cactuses and Golden Pothos plants (but it can burn plants easily if you do it too much; it's harder to burn plants with ammonium sulfate).
Rubber figs are said to like lots of bright indirect light (but not direct sun), but they'll generally survive on low light.
Remember, you can take leaf cuttings of rubber plants to get new plants (so if you want a backup plant, that's a way to do it). The leaf cuttings may or may not lose their variegation, and some people think that although they grow roots they don't grow leaves (but they do grow leaves at least some of the time, from videos I've seen).
If you want a plant you can (and should) water a lot, I recommend spider plants (Chlorophytum comosum) in pretty bright light where they will grow vigorously (bright light might make their tips get crisp sometimes, but they really grow nicely in a south window with plenty of water). They grow a lot more slowly in lower light, and probably don't need nearly as much water then, either.