Back up your data  (3rd party apps ) first as you will loose them and follow the procedure where you have to clear not only dalvik-cahe but also system and data sections (I cant recalled whether our CWM has the option to do format system/data) This is because what is not told to you is that since the data folder folder was increase from 4G to 7Gb it will overlap some remnants files and this causes problems later.(My ROMs are always TWRP recovery except for KASTY M9Pro which is on CWM)

It is either you reflash the 2 - 3 X to clear all the rubbish left behind after every flash go inside data folder and delete anything you find in there or install some system maintenance app( I personally found 600MB of oprphan files in some hiden cache folder that is not visible to us after I upgraded from JB 4GB data to KK 7GB data, since my device not performing well and a lot of FC app after I cleared the hidden cache folder and did another reflash using the same copy of fiirmware did the poblems go away.

To answer your question under normal circumstances IF upgrading from 4Gb JB to 4Gb KK it shouldnt be a problem at all but since admin has increase to 7Gb without warning us of the consequences (this is through my trial and error)you will have to go through an extra step or else you might say that the KK ROM is rubbish (thats what I thought in the first place)

This holds true if admin decides under pressure from users to go back to 4Gb, the flashing have to go through this extra step.I hope he doesnt since we have plenty of real estate 32Gb!!