need help dont understand?

[shoem]

i got my ph test pen yesterday and checked all my nute resovoirs. all were good but my flowering nutes. which are

Sensi bloom A&B
Big bud
Fulvic gold

When i checked ph it said 4.1? I was in shock because the plants look great not a yellow leave NOTHing. I added some ph up went 4.3, added about double the amount and the ph test read 1.3?? makes no sense.
So i emptyed and put new water checked it 6.8 i then added all nutes 900ppm and ph perfect 5.9 so i put it to work.
Today i went to check all resovoirs and all good EXCEPT the flower resv. again reading 1.8 what the fuk is going on also the water has a light yellow color. whats the deal. i posted som pic of room. a

 

[t@intshredder]

Are you using Big Bud powder or liquid?
If powder, I've noticed that you should check pH about an hour or two after you add it as the hydration lowers pH like mad.
Also, the Sensi A & B will lower your pH quite a bit too.

 

[shoem]

Are you using Big Bud powder or liquid?
If powder, I've noticed that you should check pH about an hour or two after you add it as the hydration lowers pH like mad.
Also, the Sensi A & B will lower your pH quite a bit too.

The powder form so your saying that a couple of hours after mixing nutes that ph drop to 1.8. also when i chek the reservoir with a liquid tester shows yellow 6.0. thats why dony understand. i thought might be big bud powder but i have been using this formula since beging flowering with no problems.
would light create a problem i noticed some light defintly hiting water for the 12 hours its on

 

[t@intshredder]

The powder form so your saying that a couple of hours after mixing nutes that ph drop to 1.8. also when i chek the reservoir with a liquid tester shows yellow 6.0. thats why dony understand. i thought might be big bud powder but i have been using this formula since beging flowering with no problems.
would light create a problem i noticed some light defintly hiting water for the 12 hours its on

I would think the light wouldn't be a problem, unless you have a very heavy visible algae problem which I'm assuming you don't. I've just noticed in my grows that Sensi A & B + Big bug lower the pH a lot.
There also is the possibility your pH pen wasn't factory calibrated. I would get some calibration solution and give that a shot.