The plastic case of the printhead is discolouring, it looks like it’s overheating or something. The plastic doesn’t seem to be degrading or cracking, it’s just a cosmetic thing.
Is this normal or common?
Not normal and not common as you are first person I have read a comment regarding this problem.
Which part?
The toolhead cover is made of three individual parts.
Can you post some pictures?
Thanks.
I figure it out. I have an AMS riser printed out of yellow PLA! I jogged the head forward to get a good photo and the “discolouration” slowly moved up the surface. 
1 Like