The chillers are single pass evaporators and in series. How can ch-1 have a higher RLA then ch-2 with all things being equal.?
Chiller # 1 runs at a higher evaporator temperature than chiller # 2.
Higher temperature evaporator = higher density refrigerant gas = higher load on compressor = higher full load amps.
Kinda-sorta like when your air conditioner on your house draws more amps when your house is hot than when it's cool.
If'n you could get the origional design specifications for that installation, I'll bet you'll find that's the way it was origionally spec'd.