Low DKH with phosban reactor

I recently added a TLF phosban reactor, I feed light, only 3 fish in 60 gal tank, every other day, feed corals 1xper week, change water 5 gal twice a week, vacuum 1" crushed coral sandbed once a week, tank is a little over 1 year old. I noticed a few small patches of green hair algae, not bad at all, easy brushed away with tooth brush, pretty much only on 2 of the live rock pieces. I figured it is leaching. I added the reactor 2 weeks ago and since I did my Alkalinity is staying low, 6.4, Before the reactor it stayed around 8-8.2 with 5 gal water change. Is this normal? Will it work it way out as the system gets used to the reactor, that HAS to be whats causing it.