Brown spots in flowering

[Weeder]

Hey again people!!
I think i finnaly did it. Checked ph from tap water that set 24 h and it was 9.4!!!! I had water in bottles that was less than 24h and the ph was lower as 8.7 or something like that, is this make any sense? I read that sitting water shouldnt change ph (diffrent temp maybe?) , anyway i used the bucket water that set 24 eventhogh they had higher ph because of the chlorine that should harm the roots ( am i right?), so i added nutes to the water (2ml/l cmag, 1ml/l bloombastic, 3ml/l algamic) and the solution went down to 7.4, i lowered it to 6.4 ph with ph down powder then i fed her and the runoff finaly was in the range, 6.8 ph.
What do u think guys?

 

[neurotree]

Hey man,
Fellow noob here so take it with a grain of salt. Standing water can change pH because of temperature but usually the most drastic change is due to exchange with the air. Depending on the partial pressures for say CO2 (which will drive down pH) at the source compared to that at your sink/house matters. Then keep in mind temps at both locations (which affect partial pressure). Usually, your pH will drift down for soft water primarily driven by CO2 diffusion into the water. This is super simplified but maybe will help.
Cheers!