Assuming that your ERC code is correct, you need to remember that your second and third JCM are added on top of the ones already in effect. So for things to work correctly, you'll have to subtract your first morph from the second and the original second from the third.

Alternatively, if you use DAZ Studio's MorphLoaderPro plugin, you just set up your first morph with limits in place, then load the second one on top of that, set the limits again and subtract the appropriate constant value, then do the same with the third morph.

I can give more detail if necessary, but it wouldn't make much sense without knowing your workflow.

-- I'm not mad at you, just Westphalian.