How to get rid of m/z 288.0941 and 166.0903 contamination of poroshell HILICz on QTOF 6545

Okay, here's a fun one. I have been having a problem with contamination on a Poroshell 120 HILICz column. 

The system is a 1260 infinity II HPLC coupled to a 6545 QTOF. I have checked the QTOF and the HPLC for contamination. The masses are only present when flowing through the Poroshell 120 HILICz column, and ONLY with a 10 mM ammonium acetate pH 9 buffer. I have checked all buffer components, and none of them are contaminated, so it's definitely something coming off the column. The abundances are very high, 10M or greater. I have flowed at low flow over the long weekend and the peaks haven't dropped at all. 

the m/z are 613.1419, 597.1623, 575.1800, 557.1758, 288.0941, 166.0903

I have only run amino acid standards, and a methanol:water extraction of human milk since opening this column. Has anyone seen these peaks before? Has anyone been able to get rid of them?

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