Diagnosing Sudden Alkalinity - Is this normal?

[IronChefItaly]

Hello everyone, I've stumbled into yet another reefing obstacle and I think I know whats happening but I'd like to get some second opinions in case I'm heading for a crash.

My Current Parameters...(value in brackets is my target)
Salinity - 1.025 (1.025)
Temp - 77.0 (77)
pH - 8.05 (8.2)
Nitrate - 1.50 ppm (1.0)
Phosphate - 0.04 ppm (0.03)
Alkalinity - 7.4 dkh (8.5)
Calcium - 415 ppm (430)
Magnesium - 1240 ppm (1300)

Relevant livestock... (65 gallons display + sump)
6" crocea, 4" derasa and a 2" maxima clam
8" birdsnest colony
10 square inches of plating montipora
an abundance of LPS

The problem... I test my parameters every weekend after i perform a water change and last weekend I recorded the largest drop in alkalinity since I've had this tank (10 months). My alkalinity went from 8.4 dkh to 7.6 where historically my values are solid if I'm not intentionally messing with them. To correct the difference, I raised my daily dosing of reef fusion (pre-mixed two part) from 7ml a day to 8ml a day. Typically I only adjust an additional ml every few months to compensate for ongoing coral growth. This weekend I test again, and my alkalinity values are continuing to fall to 7.3 dkh.

The question... I'd like to interpret this sudden demand increase as a result of booming coral growth but I am slightly concerned that something else more detrimental may be the cause. Is it reasonable to expect to see such drops in alkalinity? I have decided to start testing every three days and I also adjusted my dose from 8 ml to 9ml in hope that my alkalinity will begin to rise. Lastly, what dkh would I start to see rapid tissue loss or in other words, the "danger zone" to avoid?

Any thoughts, advice or experience would be highly appreciated and please feel free to ask for any other details. As always, thanks for reading!