Use of programmable gain amplifiers in ADE7878A

Hello 

I'm using ADE7878A. I have a question regarding the use of programmable gain amplifiers integrated in that IC. 

Suppose i develop a 3 - Phase Energy meter using that IC (ADE7878A)  and i connect 3 different load L1, L2 and  L3 to respective ADCs of the IC. All load has different current at a time such that current in L1 and L2 are approximately same but current in the L3 is so less that it can only be detectable at when PGA = 4. 

But datasheet of that IC says that we can't change tha PGA of Individual Current channels. so how the above condition can be implemented using ADE7878A ?