Does the WaterGuru SENSE measure Salt, Phosphates, Copper (CU) and Iron (FE)?

No. 

The SENSE S2 with the C5 cassette measures 5 water chemistry values: FC, pH, CYA, TA (Total Alkalinity) and CH (Calcium Hardness).

The SENSE S2 with the C2 cassette and the SENSE S1 with the S1 cassette measures FC and pH.

In the WaterGuru app however, you can enter your own results (from a pool store or your own water test kit), for Salt, Phosphates, Copper and Iron into the WaterGuru app yourself!

Here's how:  How do I manually enter my TEST results in the WaterGuru App?

Once you enter those values into the WaterGuru app, indications of whether those water chemistry values are either High, Low or Normal (Balanced) will be displayed.  If the water chemistry values for Salt, Phosphates, Copper and Iron are either high or low, you will see Advice showing you how to resolve the issue.