mid level filament started skipping and stringing.  

RE:

Difficult, could be everthing including but not limited to: partial clog, idler tension, grub screw on extruder motor shaft, damaged PTFE, debris in extruder, damaged nozzle, wrong temp for filament, damp filament, extrusion settings, dirty print bed...

If you provide some visual clues (pics and/or video) that would be helpful.

RE: mid level filament started skipping and stringing.

today i start printing, its like this. last week the first layer and a few layer after still okay. now even first layer seem to have this issue

RE: mid level filament started skipping and stringing.

The blobbing looks like a clogged nozzle but could be an indication of too high a z-offset. The t shaped print definitely looks like your nozzle is too high and you're not getting enough squish.

Cheers

-Bob

RE: mid level filament started skipping and stringing.

I would do a cold pull, just to be sure. Maybe its really just a partial clog and that would resolve it. In case it is a clog, I would recommend optimizing your print settings though, it could be that your hotend temp is too low or the retraction settings to aggressive. 

RE: mid level filament started skipping and stringing.

already done the cold pull, able to print like half the model then same issue occur on the model. guess its not my settings on slicer as this happen even when i print using gcode thats available on card provided by prusa. for retractions, as I'm new i haven't touch the retractions setting before. just using the standard setting. i just adjust the setting for support. any suggestions for retractions setting?  this picture attach is the whistle model in the SD card.

RE: mid level filament started skipping and stringing.

To me this still does sound like the hotend settings being too cold. Keep in mind that different filaments, even if they are all PLA. Especially if they are PLA in fact.
I would recommend printing an temperature tower within the recommended temperature range, but starting with the hottest and moving towards the cooler side. 

Have a look if you manage to complete the tower or if you see clogging at some point. Check at which temperature it clogged, set your hotend temperature then to 5 to 10°C above that temperature and then try something a bit longer with many retractions, eg a Benchy, with those settings and see if it fails. You can also try to print whatever you wanted to print as long as its not too huge.