Lithium Ion Battery Capacity: Discharge Analysis
Yes, it is normal for the resting voltage to drop below the charging voltage. 

When charging a Lithium-Iron-Phosphate cell the voltage will gradually rise as the stored charge increases, then rapidly climb to 3.6V and over as it reaches full charge. This rapid voltage rise is a result of the battery running out of places to store charge, and will not be sustained when it is resting. 

In a series pack one cell may reach full charge sooner than the others, and then its voltage could rise to over 4V before the battery reaches peak voltage. To prevent this you should put a 'balancer' circuit across each cell to bypass the current when the cell reaches 3.6V. When all cells reach 3.6V you can stop charging because the pack will be almost full. Alternatively you can gradually reduce charging current to zero while staying at peak voltage, which might get an extra 10% or so into the battery.

In the example plot below the green line is charging current, the red line is voltage across the cell, and the blue line is absorbed charge. You can see that very little charge is accepted after reaching 3.6V, and the resting voltage soon drops to 3.4V after charging current is removed.