Alkalinity and calcium troubles, could ATO ph be it?

[polyps707]

My ATO waters ph is 5.1, I calibrated my BRS ph lab prob and tested the ATO fresh water. My question shouldn't the ATO water be 7 ph neutral? RODI is a spectra pure 5 stage, 1 RO membrane, 1micron sediment filter, carbon, DI, and silica buster. TDS reads 0 tested with three different TDS meters.
Does this water drop my ph of my aquarium? I'm still having a hard time raising my alkalinity and calcium. Thanks

110 gal & 40 gal breeder frag tank both connected to 40 gallon breeder sump with skimmer, bio pellets 2 cups, GFO 1.25 cups, high capacity activated carbon1.25 cups all in canisters.

Magnesium is 1380 salifert
Alk 7.4 salifert& Hanna
Cal is 430 Hanna & salifert
Potassium is 380 salifert
Nitrate .5 ppm Red Sea & Nyos
Phosphate 15ppb not converted Hanna phosphorus

BRS doser 1.1 ml for BRS soda ash and calcium chloride recipes. They are dosed at night one hour apart from one another when ph drops. 6 minutes each x 2 for total of 24 ml, I measured the liquid for 12 minutes and the doser's were dosing at 1.9 ml @ minute.

Livestock 20 acropora sp frags, 30 soft frags on plugs.
Fish- bat fish (small right now:/ ), 10 other medium sized fish.

 

[Diesel]

Nope, RODI is always low in PH.
As your water evaporates in your system the ATO will fill up the lost part but it will not lower the PH as it just replaces your water and not salt.
If you don't replace your salt level will go up from 1.025 to maybe 1.030 if that happens your PH will raise as well.
Ok if that wasn't to complicated yet this will...........
Due to your skimmer sucking air from your room and on any given day when windows and doors are closed your Co2 in the room is close to 1000ppm
due to that # your PH can drop in your water, Co2 makes your PH drop if it will be mixed in your water.
Now bringing your airline outside from the skimmer than it's different and in many cases your PH will balance out around the 8.2 mark.