mitubishi PUHY-500YMF-B SUPER Y

I was wondering if any body could help me with the above unit which has three fan coil units connected all are 250 in size not sure of model number.only one of the units is cooling well while the other two are cooling but not so well as pipes are not sweating.The indoor expansion valves were adjusted manually by the last contractor.unit runs on 407c and all three compressors are running any suggestions on how to make it cool ,and does adjusting the valve help as it is already loose,or is there a right position for it??Al level reads 0 but gas pressure is 70psi with all three compressor running and suction pipes outside sweating well.Any suggestions would really help????:D

The indoor units continually monitor the indoor coil temperatures & calculate the superheat.
Then adjust the LEV expansion valve opening to maintain target super heat.

In your case the LEV expansion valve has been manually set possibly by part removing the LEV motor head.
So in this case the unit is unable to correctly adjust the LEV a control super heat.

The system may be about 10 years old & the LEV motor heads may have failed in a locked possition so I would suggest replace all indoor unit LEV valve motor heads.
Then each indoor unit will control SH correctly & overall system performance will be improved.