I'm kind of curious as to why the PH is still so high as it looks like you've repotted recently into those red pots. When my buffers run out of the soil I repot as the plants are ready for it anyway and the fresh soil sorts out the earlier ph issues. My soil is buffered to a ph range of 5.5 - 6.5 and I get 5 weeks or so out of it before it starts to deplete.
I'm wondering what soil your using as to what range of ph it is buffered to?
Love your spead sheet too, very efficient