Yellowing tips of leaves

[illmatik]

Noticing yellowing leaf tips on all of my plants today. I'm on week 4 of veg. I'm running Coco/Perlite.

Feeding daily with CalMag and Sensi Bloom Coco at 50% the recommended amount. PH on my water is around 6.1.

This is my first grow so I can't tell if I'm over or underfeeding here.

 

[MIMedGrower]

Good time to run some fresh water through to clear out the excess and then feed a lower strength dose.

 

[Judaz]

Seems more of a nutrient lock out issue. Time to flush

 

[illmatik]

I've always read that Coco shouldn't be flush until the it's ready to harvest and to never run straight water without nutes. Maybe I'm not fertigating frequently enough?

 

[illmatik]

Also can this be light burn/light stress? My LEDs are pretty close to the canopy, so I brought them up this morning. The leaves with the yellow tips seem to only be the leaves which are direct shot of the lights. The ones off to the side and the ones that are blocked by other leaves don't seem to have the yellow tips.

 

[Aqua Man]

Typical signs of nute burn. Deep green leaves tips burning and some slight clawing. I would also as @MIMedGrower said flush some ph'ed through and light feed right after. Then dial back the nutrients about 25%.

 

[illmatik]

I find it strange that I'm getting nute burn this late in the game but I've been using the same nute mixture since they were transplanted.

The one thing that has changed recently is that I've been feeding from a reservoir. I do notice that as the reservoir starts to get close to empty, the water changes a darker brown color. Maybe I should check the ppm of my water as it starts to deplete as maybe the nutrients are getting out of balance and more concentrated as the reservoir empties?

 

[Judaz]

Ohh yea, especially if you are recirculating and you say water is going down. Plants usually use more water than nutes. So what do you think happens to ppm if you take out water but keep the same amount of nutes?

 

[illmatik]

No recirculating. Just drip to waste. It takes about 6-7 days for my reservoir to deplete and I noticed the yellow tips on about the second to last day. Just wondering if my nutrient mixture is changing as the week goes on. I will definitely monitor this next fill. Unless I messed up the last nutrient mixing I can't see how my consistent nutrient mixture for the last 4 weeks would now cause burn when the plants are 3.5 ft tall.

 

[Aqua Man]

Evaporation my friend. It will make the solution stronger as time goes on and if not agitated well will compound the issue. Add to that the media can build up in nutrients over time and I think you have your answer

 

[illmatik]

Yup! I should know this from my experience with saltwater fish tanks. The water evaporates, the salt stays behind.

I have a mixing pump in my reservoir that I will run more frequently. I'll also start to monitor the ppm of the reservoir as time goes on and adjust by adding some water if I need to.