ppm's Going Up wks into Flower? DWC little/no water uptake

I have a ton of DWC bins going, and all ppm's were going down at a rate of about 10ppm per day or more, so I was going to raise the ppm's in all bins, but now suddenly the ppm's are going UP, even in a lot of bins that hardly have any water uptake at all. How is that even possible?? Now I don't know what to do, or if there's a problem going on, or my truncheon's broken although I don't think that's likely. Or maybe I'm just going insane, it doesn't make any sense to me.

EDIT: 6 wks into flower, I have no idea why that was omitted

Get the truncheon calibrated-- then try again... adjust the pH... but if the PPM's are going UP but the water level is the same-- your truncheon is F**'d.....
Dump and change your solutions so you know they are right on track, and get a new meter!!!!!

I have over two dozen DWC bins, dumping and changing solution takes longer than I think you realize. Oh by the way average EC is 1.5, and pH is almost scary stable at 5.75/6.0.

I have a 6 pot system with a 30 gal reservoir, same issue it's not your meter, I have found that using a root enzyme to keep the roots fresh and healthy raises the ppm, they just are not eating as much as usual, mine are healthy and when my ppm raises to what i believe is a unhealthy level I'll add some water, I do have some droopy leaves, but only on one side of one plant near my AC... at about my 5th week flowering, dark green, i thought i was over feeding them but i might be on the light side of phosphors, or potassium, so in my case I'm raising my ppm 200 - every 3 days until i hit the 900-1000 mark I'm at 740 - 810 bit low for my 5th week but again no signs of yellowing and/ or starving..
I had the same question.. so I doubt it's your meeter..