The spoilers found in below website and video of the link is already posted by one of the fan
http://www.serialxpress.com/upcoming-story-7626-a and
http://www.latestgossipwu.com/ek-shringaar-swabhimaan-t
Where as Naina goes to store room for some work were she gets the organic color brought by her.
Naina thus finds that some one has changed the colors to trouble karan and thus gets doubt on sandhya
I personally feel if sandhya does anything its boz of Nk insistence then how she changed the organic colors does Nk don't know that it will effect his own son as far as I think NK doesn't know anything related color change and medicines becoz he cares for his son best example engagement function he asked nirmala about karan safety.
Naina doubts over holi disaster and as per new promo she comes to know about expired medicine...
Yeh Surely this will lead her to sandhya but she have to wait until she collects the proof regarding that and one more thing in interview Kunal said that he will talk to his dad by his mom request, I wish nirmala and meghna relationship should be smooth in video also they showed like that only and naina against sandhya shouldn't backfire her because sandhya is more evil.
Bond of both sisters will lead to find the sandhya mystery I think that will be the next twist.