Your GH, both the Ca and the Mg portions are just fine for you to leave the tank for several weeks or a month. I sure would not add GH booster to that.
Enjoy your trip.
On a slightly different note. I think it is kind of an odd thing that we consider phosphorous a "macro" nutrient when the use of phosphorous is often well below the use of other nutrients like Ca & Mg.
A lot of the way we think about fertilizer comes from plants growing on land, and soils might be short of Ca or Mg, but MUCH more often they are short of N, P, K, so these three are macros. Carbon is not even considered, since land plants are able to get their carbon from the air.
In the average aquarium the water is supplying the Ca and Mg in reasonable quantities, so again the N, P, K are the 'big 3'.
Actually, carbon ought to be on that chart, when you are trying to figure out aquatic plant nutrition.
Per Diana Walstad, Ecology of the Planted Aquarium, aquatic plants are about 40% carbon by dry weight, so that carbon is needed in amounts over 20 times the nitrogen requirement.