What's the reason for most of bollywood's big films flopping over the last year?

many of these films have flopped at the Indian BO despite having commercial casts and big directors. Films like CC2C,Kambhakt Ishq,Blue flopped despite the presence of one of India's biggest super star viz Akshay Kumar. The latest examples of big flops have been Kites and now Raavan. Kites despite having the Rakesh-Hrithik father-son duo tanked. And Raavan has been a major disappointment despite being a Mani Ratnam film. Even My name is Khan didn't particularly do well in India despite the winning trio of SRK-Karan-Kajol. Is the taste of the Indian audience changing?