It is probably too warm or not enough air circulation. If you can't start to harden it off now (they really are as hard as nails once outside) and you have access to an electric fan then give it an hour or two every day in the air stream if you can. Just check, if it is currently warm and dry, that you haven't got something like the dreaded spider mite on it. This pest, and its cousins can appear even at this time of year and it may have been imported from its place of origin. A close examination, preferably with a magnifying glass would tell you.

I agree about too warm - the growth looks too long and sappy. This soft growth would not survive the cold winds we've been having, but I agree the best thing to do is harden it off gradually and put it outside.