She did tell me that I needed to get down to the 50 ng to be clean, so I don't know what they are doing because an assay screen wouldn't show the level right?
Exactly. Assays have no ability to give a quantitative analysis like Ive already stated. A GC/MS has to be performed in order to obtain quantitative values. And the GC/MS does not have a 50 ng cutoff threshold, so theres yet another example of the P/O not knowing what the hell s/he is talking about.

I am drinking Smart Water and Powerade Zero, will that help or is fluid fluid when it comes to these things?

Fluids like powerade or gatorade are more helpful than water because they help keep the S/G (specific gravity) within satisfactory ranges. S/G is tested along with creatinine in order to determine an overly-diluted sample. Drinking a bunch of water causes the S/G and creatinine levels to take a nosedive and thus sending up the "diluted" flags at the lab.