help with nutes???

ok, so i have ben havin problems with my ph.
i have jungle growth professional mix soil.
i am 3 weeks in of flowering, with 2 and half month veg.
my problem is i have ben losing leaves left and right from the the bottom, workin its way towards the top. ive ben using tap water and im guessing the ph has ben all messed up, there for lockin up my roots from takin in any nutes. so i went out and got some good water grom glacier out of the machine, is this water good enough?? and i just purchased some big bloom and tiger bloom. when should i start to add these.??
 
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