It's natural. A lot of rexes will defoliate in winter and sporadically send up new leaves and drop them throughout winter. Color change is another thing they do as well. With more intense light and perhaps warmer weather, they will color up once again.

One of my favorite rexes is Can-Can. The new leaves are typically silver-grey but through the summer they will start getting a pink tinge to them. As fall approaches the leaves will get brighter pink and by the time I move it back indoors for winter it is a very dark pink - almost going to a red. It does this every year without fail. By early spring it is usually leafless and the cycle begins anew.

Thank you...I wasn't sure, with this being my first Rex. Last time I tried one was perhaps forty years ago (and as a boy, I lost it during winter). I waited a long time to try again, didn't I ? Many orchids and other tropicals in between then and now.

Yeah, 40 years to try again could be considered a long time. It's all good though. Plants come and go but it is up to us to figure out what went wrong or if it was just a weak plant. Then we can move on and find a new interest.

i have Christmas, but not a mini. It goes silvery when there is not enough sun. though they usually say NOT to put it in a sunny window, i keep it in the western window in dappled moving shade, it is a foot from the window and gets a little shaded, but does get sev hours of late afternoon sun. the color is brightest pink when it gets at least 4 hours of dappled sun. I got it in florida where the light is very intense - and i kept it there in south-west exposure in winter - it did very good. all my begonias get sev hours of dappled sun in SE or SW windows, no sheers , just somewhat shaded by taller plants overhead.