2GB ram has higher temperature than 4GB ram

Just buy one more 2nd hand server. Everything are the same including the OS, except one using 8x2GB ram and the other using 4x4GB ram. I found out 4GB ram has lower temperature than 2GB ram. I guess is because in 4GB-ram-block server, it has more space between each ram (because i only used 4 ram slots, in 8x2GB ram server, I used all 8 ram slots), but is it the real reason?

These are from 4x4GB server:
Ch. 0 DIMM 0: +57.5°C (low = +127.5°C, high = +127.5°C)
Ch. 1 DIMM 0: +58.0°C (low = +127.5°C, high = +127.5°C)
Ch. 2 DIMM 0: +57.5°C (low = +127.5°C, high = +127.5°C)
Ch. 3 DIMM 0: +54.0°C (low = +127.5°C, high = +127.5°C)

These are from 8x2GB server:
Ch. 0 DIMM 0: +75.5 C (low = +127.5 C, high = +127.5 C)
Ch. 0 DIMM 1: +70.0 C (low = +127.5 C, high = +127.5 C)
Ch. 1 DIMM 0: +77.0 C (low = +127.5 C, high = +127.5 C)
Ch. 1 DIMM 1: +65.0 C (low = +127.5 C, high = +127.5 C)
Ch. 2 DIMM 0: +75.0 C (low = +127.5 C, high = +127.5 C)
Ch. 2 DIMM 1: +55.5 C (low = +127.5 C, high = +127.5 C)
Ch. 3 DIMM 0: +72.5 C (low = +127.5 C, high = +127.5 C)
Ch. 3 DIMM 1: +53.0 C (low = +127.5 C, high = +127.5 C)