Your magnesium is too low. It has to come up between 1350 and 1400. I would only dose that right now, using Mag Chloride and Mag Sulfate (7.25 cups Mag Flake & .75 of a cup of Epson salt in exactly 1 gallon of RO/DI). Using Jdieck's Reef Calculator, you can find out exactly how much you need to add.
http://home.comcast.net/~jdieck1/chem_calc3.html
Then whatever that number is, cut it in half and dose the first dose today, and the second one tomorrow.
I have some already mixed up if you don't have access to what you need and want to pick it up today. It looks like I have 3500ml on hand.
Once Mg is up, it stays up a long time. And I have a feeling you'll see your alk rise up as a result.
Because your reef is doing so well, I wouldn't use my kalk yet. Maybe 1 gallon over night each night, watching the tank closely for any response. Look at the corals, the color, the water clarity (and of course your numbers, but almost secondarily) to see how everything acts to the new method. There's no reason to rush this one.
I dose twice a day 4oz of each product (8oz ea per day). I use the same little measuring container to dose. It gets a build up of calcium deposits on it, could this be a problem, maybe the Alk precipitates on the cup and I’m actually dosing less?
You should have two different cups, and when you dose, pour VERY slowly into an area of high flow. It could take as much as a minute to pour 4 oz in the tank. You want it to add gradually like smoke, not in flake form as that precipitated into a solid and is essentially inert.