pH buffer? needs to last 3 weeks

Hey guys,
I have to leave my grow for 3 weeks.

I have LED's so it won't burn down and its in a tent with a large tray under it if the pumps malfunction
I made a reservoir to pump nutes in with an overflow so it will get topped off to 6 gallon mark every day with water

I'm using a Stealth Hydro Bubbleponics system (I know, cheaper to build your own, etc.)
with Stealth Hydro Nutes
They nutes balance pH pretty well but I'm worried since I'm gone I don't do a res change every now and then it will go into nute lock from pH
The reservoir is aerated and all and has cannazym to prevent root rot

Sooo question is... how to I buffer? Is it possible? Should I make my res acidic to counteract?
What will happen if I leave it for 3 weeks? I don't want to kill it

thanks + toke on, dudes

Anybody out there?

according to the grodan website throwing a half cut up lemon in your res will help keep it down while on vacation. I never tried it. Better measure how much acid it lets thru. GL.

That is an interesting idea... I wonder though, might the lemon grow mold or start leaking particles that clog my pump?