Unexpected base line (GC FID)

Hello everyone!! I am new to this forum

I have been given an Agilent GC/FID 7890B and asked to set a fatty acid analysis method.

The thing is that I have been having problems with the base line recently and since I am new to GC chromatography I don't know what is causing it and how to solve it.

Column: HP-88 60 m x 0,25 mm, 0,2 µm ; Oven inicial temp: 125 ºC ; Oven max temp: 220 ºC ; Carrier gas: He ; Detector: FID 260 ºC ; Sample solvent: n-Hexane

If there is anything else important that I should mention let me know!

So, a month ago this is how a run of a 10 ppm 37-FAME sample would look like:

And this is how a 10 ppm 37-FAME sample looks like right now:

And if this is any helpful here is an image of a Blank sample on the same run as the previous sample:

I would appreciate any help or criticism !!

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