Little help with dwc please

Ph is at 5.7, turned light down lower but still plenty bright. Water temp is 66 degrees, ppm is 1050, plants are five weeks into veg, three different strains in three different tents. Ec is 1.9. Root growth has slowed and the yellowing has happened within two days. Roots look healthy, humidity is at 65, also using Hydroguard and Calmag at recommended dose. Also have four inch air diffusers in each tank with a pump with more than enough air for the root zone.

1900 ppm sounds high to me. I only ran DWC/rDWC for a few years, but I don't think I ever got that high. I think I may have pushed 1600-1800 mid flower one run and I remember that being overkill. Could just be over fed or locked out.

i dont grow in dwc but the yellowing started within 2 days? it sounds like your plants cant uptake nutrients it sounds like you have some sort of nutrient lockout happening...

if i was you i would buy some fresh base fertilizer and cal mag and give them a fresh nutrient feeding.

what i would feed a mature plant is 600 to 800ppm's of base fertilizer and 100 to 200 ppm's of cal mag and call it a day.

sorry are you say fresh batch I switched it out lower ppm to 700-800 now it is some lockout what would cause a lock out ?

When was the last time you swapped out all the water in your reservoir with fresh? It should be done every 2 weeks at the longest I believe.

what nutes you feeding it? 1.9 is way too high, those leaves won't get better, cut them out.

I haven't ran across many DWC plants that wanted higher than a +1.0EC (or 5-600 PPM) solution in veg, without a sealed\dialed in room anyway. Not even massive plants with a 1 inch stalk. Or any that ever really need calmag supplements.. not even with filtered water.

50% of the time I see people having problems, especially in veg with DWC now days.. it's because their PH meters are off one way or the other. Double checking against a sample tube with the drops is always a good idea.

It would help a lot to diagnose if you verify your PH is actually in range, and keep track of the water levels as well as the EC to see how much they are really eating\drinking.

Also, if you used a bigger res with more capacity. So the PH doesn't fluctuate as rapidly, which is enough to cause lockouts on its own, even if its still in range.