Prodibio/carbon dosing/alk question

[Proteus]

OK first off

Sg--35ppt
Po4--0.03
No3--0.25
Alk--8.3
Cal--430
Mg--1280

Dosing tropic Marin baling salts
6xt5 ati

OK I am/was dosing prodibio biggest, zeostart3,zeofood.
Po4 was at 0.01 so I guess that can be called ultra low.

I know that with zeo I need to keep alk below 8. But found ime that millis preferred above 8. I started to see burn tips on a couple acros. Which I know is from elevated alk, so I decided to drop zeo start and go back to rowaphos.

So question is

Is the low alk desired because of carbon dosing of because of bacteria?

From what I've been reading some bacteria strains don't multiply in higher alk. I'd like to keep dosing biodigest but not if I need to lower alk

Thank you in advance