Ok, what is the Name of your grow tent? Is it an older style tent or have you grown successfully in it before? Hydrohut made one set of tents that caused growers plants to die off due to a weird gas the tent or the poles gave off. You don't see many of them anymore is it an issue that the company has resolved. Just trying to cover all the bases.

Now, you seem like a go getter to me. Call Britta and ask them what chemicals they use in their filters to "soften" the water and exactly what is removed from the water during this process. I believe the answer will not only surprise you, but also cause you to switch the water you are using to either plain tap (sometimes it works well in hydro apps; just depends on your water. Personally I would use RO or distilled water and CakMag for hydro apps.) Definitely lose the Britta filter imo.

PS...if your ph is going in to e and f at 6 but coming back higher thats a different issue. is it?

good luck