Upper fans yellowing 3.5 weeks into flowering

[OldMedUser]

I have what I think is a good idea about what's going on with this plant and lesser so on the other one also grown in soilless mix with AN Connoisseur, Big Bud, Rhino Skin and I think too much CalMag.

The upper fan leaves attached to bud sites are yellowing but older and lower fans that aren't are fine and the fan across from a yellowing one can be fine as well. I'd not worry if a few, or even many of the older, lower fan leaves, were doing this almost half way thru flower.

They are yellowing back from the tips in what looks like low N and/or Mg. After they are completely yellow the tips start shriveling up and turning brown while remaining soft and pliable. So it's not toxic salts buildup with thick, crispy dry, brown leaves.

After consulting my grow bibles and looking for similar symptoms in this forum I'm thinking that the calmag I've been giving with each feeding may have led to a buildup of Ca and that is interfering with Mg uptake. I gave it another heavy feeding of the usual but instead of using calmag I gave it 1 heaping tsp/gal of epsom salts instead. The symptoms hint at lack of sulfur too so if it is then I've covered both bases with the epsom salts.

It's Technaflora MagiCal with the following ingredients.
N - 2% Nitrate Nitrogen
Ca - 3.25%
Mg - 1.25%
Fe - 0.11%

The Ca seems higher in proportion to the Mg to me than it should be but I'm not sure. I got this one instead of the one AN makes because AN was over twice the price and I figured I needed some CalMag and any old CalMag should do right. Penny wise, pound foolish maybe? That was 5 or 6 years ago so maybe it's gone bad?

It was about 36 hours ago that I fed them and if it seems to be progressing further by light's on tonight then I plan to flush each 4gal pot with 5 gal of town water tomorrow that I will have to go to a friend's to get today. The plant that is the worst and is the bigger of the two has been in that pot for at least 4 or 5 months and the other about 3. I had them on half rations since the new year to keep growth slow and just got around to getting them in gear about 6 weeks ago.

The greener looking stuff in the front with the nicer buds is from my NL girl that is in DWC using the same nutes at about 1200ppm and barely a yellow leaf on it. It is a re-vegged girl that nearly died and has come back great.

I'm fairly good at diagnosing problems like this and I'm pretty sure I'm on the right track but maybe it's something a bit different so I thought I'd toss it out there and see what you guys think.

L8r

 

[Robert Celt]

I am not a hydro man but had a similar problem with my Cherry Bombs in organic super soil. After much research and questioning on here, I determined it was due to the molasses I had been adding to my watering during early blooming. The Cherry Bombs seem to be more sensitive to pH and nutrient levels than my other Bomb Girls. The excess potassium along with a slightly higher pH can cause magnesium lockout with then leads to calcium lockout.

After discovering this, I flushed them with distilled water and when they needed water the next time I added Epsom salt and within 7-10 days the problem was solved. Not had an issue with the Cherry Girls since. The THC Girls on the other hand, I almost pulled an UncleCannabis and dried one on the vine while I was away with family and didn't see to watering her LOL

 

[OldMedUser]

The hydro one is doing best of all TC. (Should have named yourself TheHappyCelt or TheHairyCelt or TheHornyCelt then your initials would be THC.

Wouldn't you know that with this last feeding I decided to include for the first time, a heaping Tbsp of molasses to each of their 4L jugs, but I don't think it's going to cause a problem. The pH should be OK because I'm using the pH perfect nutes but these plants are about a year old already so I wasn't expecting a lot out of them.

The two in pots are the ones with the yellowing, one much less than the other and they are two different strains so it's got to be something going on with the feeding or possibly too much of one nute blocking another.

Just went down to have a look and I think it looks a little worse so I'll give them a flush tomorrow and a 3/4 feed right after.

L8r

 

[Robert Celt]

Morning OldMedUser.

My wife would probably agree with TheHornyCelt LOL

 

[NuttyProfessor]

looks like iron deficiency

 

[OldMedUser]

I ruled out iron Prof as the leaves start going yellow from the opposite end of the tips and starts from the petiole with low iron and these are yellowing from the tips. It also affects the youngest growth or the tops first and the buds are looking fine.

If I can get the flush done today then I'll have a fresh charge of nutes in there to hopefully balance everything out again.

I prefer to figure out precisely what's wrong and fix it but that's not working it seems so a flush can wipe the slate clean and to me is defeat.

I'm beginning to wonder if it isn't something to do with the buffers used to make pH Perfect technology work tho I have no basis in fact to suspect that. I've been feeding heavy but maybe not heavy enough for all the budding going on.

Almost 4 weeks into flowering now and they are not doing as well as the DWC one at all. They are old plants and have been in those pots for a lot longer than is usual.

L8r