Energy Savings Mode with multiple monitors

I have 5 Dell monitors running on 2 x GTX 650 Ti Boost 2GB cards in the following setup:

Card 1 - 2 x P2412H using DVI ports

Card 2 - 1 x P2412H 1 x U2412M using DVI ports and 1 x 1907FP using HDMI port.

For some reason when Energy savings mode (ESM) starts, all but one monitor goes into ESM, one of the P2412H monitors on card 1. It dims, ie. blue light stays on, but doesn't go into ESM properly.

2nd question is why does the U2412M monitor go into ESM a bit slower than the P2412H screens?

Note: Drivers are up to date, have tried various ESM plans, etc.

These are not huge issues but still like to know why and fix if possible.

Thanks for your help!