Brown aerial root tips on Brassavola

[Roberta]

Another thought... just use your Peters formula (which will probably take care of dropping the pH of the tap water, also making the calcium and magnesium available. If the hardness is calcium carbonate (most likely) then a small pH shift a shade below 7, which the tap water fertilizer will do, takes care of everything in one fell swoop. Your TDS is low enough that you don't need a whole lot of phosphate (the middle fertilizer number) to put the pH right where you want it.