I have a Dieffenbachia camilla, sometimes called 'Dumb Cane', that I got about two years ago. It seemed like it needed a new pot so I put it in one size larger, and it did very well: it started growing new leaves and looked healthy. Not knowing much about plants, a month or two after I put it in an even larger pot, thinking it would help too. Now that I know more about plants, I know this was a bad idea as it wasn't ready for a larger pot. Some of the leaves started falling off and the leaves look thin and spindly. Also, new leaves grow on fairly slowly, and sometimes before becoming mature they turn yellow and fall off. Also, many mature leaves have also yellowed and have fallen off, making the trunk look a little bare.
Question. I was thinking that perhaps it's in too large a pot, as it started to decline when it was put in the larger one. It's been in this pot for a year but barely grew, so would it be a good idea to transplant it back to the smaller pot it was in before?