The most likely reason for this is to keep the viewers from changing channels as Colors also launches at 9pm Sanskaar - Dharohar Apno Ki.
Both shows have a Gujarati background, but after Monday, Amita Ka Amit will be competing at the 8.30pm slot with shows such as Madhubala, Ek Hazaaron Mein Meri Behna Hai, Qubool Hai and Taarak Mehta Ka Ooltah Chashmah.
On the other hand at 9pm, HJNH will face competition with Colors new show.
UPDATE: Schedule for India and Rest of the World shows no HJNH this Monday (21/01/13) too, not sure if they've not updated it or there actually will be no episode.
www.setasia.tv/en-gb/schedule
www.setindia.com/schedule.php