Using Hesi PH- Growth during 3rd week of flowering?

I stopped by my local headshop today, and i accidentally bought a Hesi ph minus for growth. I guess that means that it has to be used during veg phase right? Would it still work during flowering? just for a watering or two. then i will be able to get the one for bloom. The strain is White Widdow, and they are growing under one 250W HPS.

thanks!

bump

It can be used anytime, the question is your PH too high?

Great, thanks! Yes. The water i use is 7.1 ph. so i guess i should bump it down to 6.5 right?