random network Performance on host, inter-host

network performance issue between host communication etc.

we have 3 esx4 host in infras.

lets say esx 1/2/3

esx 1  has VM A B C D

esx 3 has VM F G H I

When copying files from vm A to F , noticed speed was 2-300 kbs

same was case for A - G around 300kbs

but from A  to H , same file was being copied at around 40-60mbs

now if i move both vm  F and G to esx 1 , i get speeds around 40-60mbs

also copying file from F to G/H/I is also 40-60mbs

i am not having trouble copying files from A  to H or I for that matter. 

all hosts are on same vlan, and same switch

im not too familiar with VMware, but looking at configs, nothing has changed on esx side or cisco switch side.