HELP! Help Identify Plant Issue - Hydro DWC

[Randomuser123]

hey there,
since my last post i learned some things with my first Hydro Grow, but now my plants look troubled again - so i wanted to ask for the feedback from this forum.

• Using LED 2xSanlight EVO-120 (2x250W) dimmed down to 40% on 120cmX120cm area. Light distance 40cm
• maintaining ph between 5.8 - 6.1
• Air Temperatur is between 22-25°C (71.6-77°F) / Water Temp 21-23C° (69.8-73.5°F) / Humidity betweedn 50-65%
• EC 1.4 (using TripartFlora, TripartMicro, TripartGro from GHE)

When i first noticed the signs few days ago i was looking for possible issues

• Nutrients should be fine with EC 1.4 (GHE recommends 1.3-1.8 during veg)
• Watertemp 21-23°C should be fine (ive added beneficial bacteria BioHealth starting yesterday TH BS WSG to prevent root rot)
• i re-checked my air pumps, which had 600l/h (158Gallon/h) air for 50l (13 gallon) reservoir and replaced them today with stronger pumps to provide more oxygen to the roots

If you guys got anymore ideas i would appreciate that.




Thanks all in advance for taking some time to help!
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[Bluey]

What are you using to measure pH?

My first guess would be magnesium deficiency which is often caused by low pH.

 

[Randomuser123]

I am using a BlueLab PH Pen to measure twice a day. Magnesium deficiency seems likely since im using the Hard Water Micro but havent added CalMag supplement yet

Tap water i use has around 5,7mg/l Magnesium and 72,7mg/l Calcium (last analysis 2022) - i couldnt find any resources on a quick research, do you know a threshold for tap water on CalMag which is sufficient without supplements?

 

[Allenpro]

Are you checking the PH after you add the nutrients and supplements?
For me and my well water I have found letting the PH drift between 5.9 and 6.2 works best in DWC, & Coco Coir. At 5.7 your outside of the optimal PH for Cal intake and adding more to the mix will only make it worse


https://www.growweedeasy.com/ph

 

[Randomuser123]

yea always checking after adding nutrients (as well as daily ph check) so i can adjust the ph and im keeping ph between 5.8 - 6.2

 

[Bluey]

How often are you doing full nute changeover?

 

[Randomuser123]

im changing the water of the reservoir weekly and after changing im adding new nutes and adjust ph

 

[Mr.furley]

First off, you are burning the crap out of them small plants. I flower at 1.4 to 1.8 so after you calibrate the EC and ph pens drop your ec to 1.0.

Secondly calcium and magnesium have a symbiotic relationship without one the other one is not beneficial. You can throw as much calcium out as you like but until you get your pH above 6.2 your plants will not absorb it, in hydro swing the ph between 5.9 and 6.3. Calcium is a inmobile nutrient which means it won't move from the lower part of the plant to the upper part of the plant hence the yellowing up top, magnesium is mobile which means if you have a magnesium problem you'll have Browning/yellowing down low.

I'd recommend to change the water and flush for a couple day with plain water pH'ed at 6.3 with the lights raised, then add the appropriate nutrients in the appropriate amount, at the appropriate pH.

 

[Randomuser123]

thank you for the feedback, i will have to be more careful with nutrients going forward. changed the water for now and see how they will respond

 

[Allenpro]

Whats the PPM ?

 

[Randomuser123]

EC was around 1.4 (im always using EC) and not sure about the PPM or what scale to use for that (bluelab pen has different ppm conversion scales, so i just use EC). But another user pointed out that EC 1.4 is too much for those. right now after water change im looking at 6.3ph and 0.5 EC

 

[Allenpro]

Are you using the 500, 640 or 700 EC scale? Either way I agree that it too hot.. Looking at the conversion chart I would say that is about double what they need if its the 500 scale. I would flush with PH water for a day and then add some nutrients starting at about .7 EC on the 500 scale. The varied scale is why I use PPM instead of EC, Well that and being old and set in my ways lol