Dracena lemon with brown marks

[kafnit]

hello,

I have a dracena lemon lime I bought a month ago.
and for unknown reason its leaves got a brown marks:

After I bought it I planted it in a new pot with new soil (with other planes).
I isn't sitting is a sunny place(dont mind the sun in the pic- is is only for the photo).
Can you let me know what is the reason for those brown marks?

Thx.

 

[kafnit]

Correction: It isn't sitting in a sunny place