Do Quest or LabCorp take a separate vial for each line item (besides CBC)? If yes, is there any concern of getting all the markers drawn at once?

Typically the lab drawing the blood knows what tubes to use for the different biomarkers on a panel.

They try and minimize the number of tubes they use because the same tube can be used on multiple biomarkers. The only time they will draw multiple tubes of the same type, i.e. serum separator tubes is if the samples are going to different labs to be analyzed. Certain Quest labs (and probably LabCorp) specialize in a particular biomarker or series of biomarkers, e.g. reverse T3 or hormones and therefore they will have to get their own tube of blood.