Leaves curling, what’s it telling me?

hello bonsai_ists
I have an Aspen cutting that rooted this summer, I transferred it into bonsai soil a few weeks later.
it has since developed this “leaf-curl”? any idea what it’s trying to tell me? it gets watered every other day or when it appears to need it.
previously the leaves were perfectly flat & round.
thank you for your feedback & thoughts,

moo.

What part of the world are you in @mooyagi?
Autumn is coming to the northern hemisphere.

actually! yes, it most certainly is getting cold here in toronto, canada.
I did hold this aspen back this year, and will be keeping it under grow light through the winter.
I thought because it rooted so late in the year, it would survive a harsh canadian winter with barely-baby roots.
hope that helps clear any confusion.