Riddle me this, riddle me that, where the heck are my phospates at?

SO I have a bit of a question / dilemma on my hands.
My tanks runs very high on nitrates . 25-50 ppm.
My setup does not include filter socks .
I have short runs of pipe with full siphon
huge skimmer for the tank. 100 gallon total volume
my live stock are 2 small clown fish.
rox .8 carbon reactor
bare bottom (so its not the sand acting as a sink)
and that is it. totally basic.

I dose 4 ml of n04po4x daily on a dosing pump .5 ml at a time.

heres the catch. my glass needs cleaning about ohhhh. EVERY TWO WEEKS!

My phospates are at 6 ppB. yes that billion.

tank is about 90 days ish old.

ARE my phosphates so low as to inhibit the carbon dosing method for heterophic bacteria from working?

ive posted some photos of the tests below. I have tested my source water after mixing to rule out any chance of a bad batch and it comes up 0 not even when viewed sideways is there any touch of pink in it.

I am assuming ( i know , not the scientific method) that my phosphates have been driven low enough by the carbon dosing to be limiting.

I can not for the life o me think where all these nitrates are coming from . I do a weekly water change of 25%.

what are your guys thoughts on this?

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