Anyone know what would cause chromium, tin, and zinc to go high in a hydraulic system. All other metals are nominal.

Chromium could be from hydraulic cylinder rods, check for damaged or bent rods.
Zinc, are there any galvanised iron fittings on the system?

As said before chrome is from cylinders or ram usually. Unusual to get tin in hydraulics but a possible source may be from bearings in the pump although another metal ie lead would be expected. Please post if you do find a positive source in the unit in question.

Since both your chromium and tin levels have gone high, I would suspect a bearing problem somewhere in your system, possibly in your pump. Zinc is normally an anti wear additive. could it be possible that someone topped off your tank with new fluid?