All you have proven is that the tube has elements that can be toxic, you have not demonstrated in any way that those elements are unstable and may readily leech into the medium (water).
Chromatographs incinerate materials then use a color spectrum to identify elements when turned to gas. You are obviously not subjecting the hose to any substantial heat source so what does that have to do with anything.
As a scientist I cannot accept that just because a material may contain degenerate elements it must be toxic.
Like I said chopping up the hose in small pieces and placing it in a grow medium with a second plant with no hose as a control is much more convincing than any chromatograph test.
BTW: Wow GCS testing is way way expensive. You really should have got a professional opinion.