Thumbs up [Q] about next release of dn3 and some problems

hello, i installed dn3 v5.2 rom and i'm very very happy with it. but it consumes lots of ram. but with cm11 it works fine. i'm not comparing or criticizing any of the rom. but can anyone tell me why it is? because my phone becomes very slow after a day usage with dn3 but cm11 still have 1.4gb left to do multitasking.please anyone tell me why like this?

thanks in advamce