:smoking: roger that on your situation,... Oh, TDS - total dissolved solids, measured in ppm's... it's actually an extrapolation of EC (electro-conductivity), so the two are directly related...
TARFU-- sorry, that's an old military abbreviation for Things Are Really F*cked Up!
.... yes, adjust the water or nute solution pH last, after all other inputs are added,...
-- yes to the Ca and Mg at full str., pH 6.3 sounds good! The fert's are pretty mild, so at 2ml/L you did last time, try 3ml/L,... ideally, if you could get hold of something with higher P-K ratio, that'd be a nice boost for the buds to come,...
... the expiration dates aren't that black and white about it's condition,.. storage conditions (warm, cold, big swings between), light, etc. can make them last longer-- or
not,..also cross contamination with other chem's will muck them up,.. best judge is your eyes and nose, if you recall how it looked/smelled when fresh!
... whiteflies-
easy kill there fortunately!