Hey Cheezy,
The best advice right now, is everything in moderation...
-next time, veg it longer - FIM or TOP the plant early on in it's life a couple of times, and then utilize Low-Stress Training techniques (
https://www.rollitup.org/advanced-marijuana-cultivation/369528-low-stress-training-lst-guide.html) to keep it's height down - since you're in a stealth operation like myself. This is what I did and I have about 20 colas on a plant that has a main stem that is over 3 feet tall, but the plant is only 2 feet tall...the main cola is actually the SHORTEST cola on the whole damn plant.
-One thing I noticed is your nutrient solutions...It seems like you started feeding FFGrow Big at 25 days into veg period every other watering. Then, a little over 10 days later, at day 38, you started giving it FFBig Bloom with 12/12 light. Like I said, everything in moderation. Cannabis likes to have smooth transitional periods...and in this case...it just looks like shock.
Next grow, try vegging for longer, feeding it FFGrow Big earlier on, but at a 1/4 of its recommended dose. Increase that throughout the veg period until your at your max dose. Then, as you approach 12/12 (like 3 feedings left on veg), start decreasing your FFGrow Big and start introducing FFBig Bloom. With every PPM of FFGRow Big you take out, add it in FFBig Bloom. I am talking about 1/8th it's recommended strength. Very little.
Then, leading up to 12/12, you gradually wean the plant off of FFGrow Big, gradually introducing FFBig Bloom...so that when you hit 12/12 you are still feeding it
a little FFGrow Big but are primarily feeding it FFBig Bloom.
Cannabis needs high Nitrogen levels during it's stretch, and I have read that feeding a lower Nitrogen dose well into flowering helps with the yields (i.e. it keeps your fan leaves from dying out too early...which keeps the photosynthetic process going as well). That said, try not to feed it Bloom
BOOSTERS until about 1/2 way into flowering - as early flowering needs a lot of Nitrogen and Phosphorus. The plant really needs potassium as the buds start to bulk up, but not really sooner.
Timing is everything and smooth transitions make it easier to time your introductions...for example, I am day 31 of 12/12, but I am really only day 21 of flowering (the first sign of sex, pistils, and calyxes). So I was giving my girls General Organics BioThrive in small doses up until 5 days ago. I am JUST NOW fully into my bloom nutrients. So the better I am able to ready the plant for change, the happier the plant will be.
In short - I don't think it's a deficiency...just a shock issue.
Give it a flush of distilled water, pH the run-off - then, the next feed, give it a bit of your FFGrowBig along with your FFBigBud but do so in lower quantities than you have in the past. Feed lightly after you flush, then gradually shift from GrowBig to BigBud over the course of three feedings.
That's my opinion! Good luck, friend!!
Smacks.