Ok....more thorough read through. What day are you at? I personally use cannazym and have found the opposite is true...cannazym helps stabilize ph, not raise it so i'm not sure that is your problem.

When did you add this metal you are talking about? That would make me wonder if perhaps something is leaching into your water. I don't know enough about it to say but I do wonder....

How are your plants growing? Happily or do they have issues? As they get later on into flowering its normal for the ph to rise daily due to high nutrient needs. Mine generally will rise about 1 point a day (from 5.6 to 6.5 in 24 hours) so that becomes something you have to deal with if that is indeed the reason.

I personally hate hydroton with a passion (it's a personal thing :wtf but if you are more than 4 weeks in your hydroton should be stabilized even if you didn't pre-treat it correctly. And if it was normal before but NOW is a problem.....that doesn't really fit with "new hydroton syndrome."