kinlam

Hi, I have been using ultimaker 2 go for 7 months and its printing quality is good so far. However, it messes up ( underextruding ) recently. Here is a test of printing 3 ultimaker robots to show the problem and the result are as below: as you can see the printing in the beginning is good and it messes up after 5mm height. I had went through the Atomic method so I know that the nozzle is 100% clean. Do anyone have the the same problem? How to fix it? Please help! lam