I have a potted one-year-old-or so lime tree, which has looked quite healthy for the past two months or so (after recovering from a winter where it lost a lot of leaves due to overwatering).
Since the outside was really cold and it's on the ledge of the (closed) window of my office, I let the heater on during one night, in addition to the usual central heating -- so when I cam back the next day, my office was quite warm, maybe 27° C.
Later that day, I noticed that two leaves of the lime tree had edges that were whitening; after a few more days, it does not seem to spread to many leaves, but it currently had 3-4 leaves showng the same sort of whitening:
In terms of watering, I water this tree twice a week, and try not to overdo it; it's on the ledge of a window headed East, in an office in Manhattan (so, recently, it's been rather cold outside, roughly freezing temperatures; but my office stays at 18°-20° C).
Should I be worried? Am I doing something wrong?