GC-MS unexpected peaks during 1-octanol quantification

Note: This experiment was performed as part of a teaching lab experiment which has concluded, so I would not be able to alter any experimental conditions. I was also unable to modify any of the variables used in the GC-MS experiment itself, but I may be able to provide these upon request. 


I would like help in the interpretation of this spectrum from experienced chromatographers, I expect more information to be required other than the spectra provided, but due to my inexperience I am uncertain what they might be. Please do point them out in the comments if necessary. 


This is a spectrogram plot performed in Mathematica of the relevant data for octanol quantification (octanol normally elutes at approximately 5.8-5.9 minutes, and did so in the positive control samples.)


The GC-MS machine was not used by any other group during the 2 days, and the only samples run on it during the 2 days were either ddH2O (with or without octanol) or sterile filtered cultures of *E. coli* in M9 growth media+glucose (with or without octanol).


All images are thumbnailed, click on the link to open a full resolution image.


Representative samples taken on Wednesday, consistent high levels of tailing. All samples are in ddH2O.


[ddH2O](https://i.stack.imgur.com/HYLEU.png)
![enter image description here](https://i.stack.imgur.com/HYLEUm.png)
[25mg/L octanol](https://i.stack.imgur.com/yxlFg.png)
![enter image description here](https://i.stack.imgur.com/yxlFgm.png)
[100mg/L octanol](https://i.stack.imgur.com/uoAUc.png)
![enter image description here](https://i.stack.imgur.com/uoAUcm.png)


Samples taken on Friday, varying amount of tailing


[ddH2O](https://i.stack.imgur.com/xzjXL.png)
![enter image description here](https://i.stack.imgur.com/xzjXLm.png)
[Blank growth media](https://i.stack.imgur.com/yAPcU.png)
![enter image description here](https://i.stack.imgur.com/yAPcUm.png)


[100mg/L octanol in ddH2O, not tailed](https://i.stack.imgur.com/6RVGB.png)
![enter image description here](https://i.stack.imgur.com/6RVGBm.png)


[50mg/L octanol spiked into growth media](https://i.stack.imgur.com/i10jz.png)
![enter image description here](https://i.stack.imgur.com/i10jzm.png)
[100mg/L octanol in ddH2O, tailed](https://i.stack.imgur.com/bmMmI.png)
![enter image description here](https://i.stack.imgur.com/bmMmIm.png)


The noise present (at m/z 59 and 78) seemed inconsistent with the column (100% DMPS) nor any of the alternatives present [on a list of possible column bleed spectra](http://onlinelibrary.wiley.com/doi/10.1002/9783527611300.app4/summary). 


Octanol's solubility seems to be 2300mg/L [as seen here](http://uwrl.usu.edu/www/doucette/6730/CEE%206730%20Kow%20lec7.pdf), and I don't find it very likely that the low solubility of octanol in ddH2O resulted in the tailing. 


What could have caused the noise at m/z 59 and 78, and why was the tailing so different despite near-identical experimental conditions?


