Phosphorus deficiency? I can fix this!

[Alaskan1]

Problem: Lower leaves started turning brown on the edges and tips. Stems started going red.

Medium/grow method: Sunshine Mix [HASHTAG]#1[/HASHTAG]

Feed: and supplements used: FoxFarm Grow Big and General Hydroponics CALiMAGic Calcium-Magnesium. I use white vinegar to adjust PH

water source: Tap water, set overnight

Strain/age: Short Stuff Mi5, 41 days

light used:Solar Storm 440 LED

Climate: Grow Tent, 72-28 F

 

[Alaskan1]

Hi All,
So I'm hoping to fix this myself. This Mi5 a week ago (see pic) had just one fan leaf at the bottom going brown, and I assumed it probably got some nutes on a leaf. I just plucked it off. At the same time, I realized my light's UVB light switch was on, and it shouldn't have been until the last couple of weeks of a grow. I switched the UVB off, and thought that perhaps I had burned the plant with the UVB.

 

[Alaskan1]

So a week later, more leaves were looking sick. Primarily lower leaves turning brown on the edges. Then I noticed that some of the stems were turning red. I've not grown Mi5 before, and perhaps this is normal. However, phosphorus deficiencies can cause red stems, and the leaves look like phosphorus deficiency. Additionally, the plant had just started going into flower, which uses more phosphorus. So, I'm thinking I have the deficiency correct. I had run out of nutes, so I watered well with ph-adjusted water (I use white vinegar and/or baking soda), letting a fair amount drip out of the bottom. Often with Sunshine [HASHTAG]#1[/HASHTAG], the PH drops after a month or so, which leads to nute lock, so perhaps this watering has helped. Well, it took a couple days to get more nutes, and of course the plant is looking worse. It's probably starving at this point..

 

[Alaskan1]

So my plan is to add some FoxFarm Tiger Bloom, along with CalMag, into my tap water I've set out over night, and see if the plant can recover. I'll check the ph of the mix, and get it adjusted to around 6.5 before I water and feed.

So any input you all might provide would be appreciated. Do you see errors in my diagnosis or proposed remedy?

Anyone else grown Mi5 who can tell me if red stems are genetic, or part of my deficiency?

Thanks!

 

[Alaskan1]

On another note, I am loving the looks of this Mi5. I normally have to tie branches off to the side to allow light into the lower buds. This plant naturally spreads out, and allows this. Very nice. I purchased these due to some post about 5 years ago by Muddy on this site. Is he still around? Anyway, Muddy praised this strain. Thanks Muddy!

 

[Alaskan1]

I calibrated my PH meter. Then added the nutes. I ended up needing white vinegar and baking soda to get the PH just right.

 

[Alaskan1]

Then I gave the girl a drink. How am I doing?

 

[TheMongol]

Fine, i use citric acid to low the ph, red stems can also happen with N def, i saw some tip burning at some leaves, you know how much ec/ppm you have given?

 

[Alaskan1]

Hey Mongol,
No, I've never tracked the ec/ppm (except when making colloidal silver). Our tap water here is quite good, so I never saw the need or had too many issues, other than needing to adjust the ph of my nute water using vinegar or baking soda, depending. So, I hadn't considered ppm. Should I? What should I be looking for? Thanks for your input! I appreciate it.

 

[Waira]

-- UVB is fine, outdoor plants get exposed full time, big time in the Sun, right?
... symptoms are pretty generic right now, hard to make a call based on those,... P defc. is a likely candidate though (red stems are not a the best indicator, too many plants have this as normal color expression).... might be some K, Mg defc.,... first thing to figure out is the in-pot pH. that will determine what to do next... if that's off, it needs correcting first, or matters will worsen, ditto for adding nutes into that situation,.. off pH can lock out certain nutes... if you're lucky, pH will be OK and it's a simple lack-of type defc,... bloom nutes should fix that,.... What you adjust to in solution has nothing to do with what happens once in-pot, too many other influencing factors in play then! Avoid using baking soda as a pH up, too much Na in there, which is toxic at low levels,...
A great tool for in-pot pH is the Accurate 8 soil pH probe-> hsoil:- long probe is the A8,... barring that, it comes down to doing the dubious run-off test; straight r-o is not an accurate measure of in-pot pH! there is an improved method and calculation here in the yellow sticky section above this one,... check it out!