Before you buy or use anything you need a better test for alk, calc, mag, ect.
"It is not at 1.7!! It is between that and 2.8." Is not a good answer/test. I agree with everyone that it sounds like a alk swing or low alk, but unless you know what it really is there is no way to tell what you need to add. And I dont use dkh, or reef builder or anything else. you can use baking soda to raise alk.
Last thing but 1.7 would kill most my corals, I keep my alk between 3.4 and 3.6.