need expert advise as i am facing issues with delta T attained in one of the site to which FM services are given

District cooling supplies chilled water with 6 degree differential(supply 4.5 and return:11 degree Celsius)

In my load side we are able to get approx 4 degree delta T only

Supply been on a average of 7.5 and return 11 degree

When referred O&M manual design which was noticed was to attain 23-24 degree celcuis supply air through AHU and FCU

Client instructs to attain 20 to 21 degree celcuis on supply air

could this possibly results in getting low delta T or is it due to some other factors