Biggest buds turning brown at end of flowering stage

[GandalfGreen]

Hey all, I've been so far doing a successfull grow of 3 girls with the '420 Carats' strain. I haven't had any issues with feeding/temperatures in the entire grow. But as I'm almost approaching harvest (about 1-2 weeks away) about 3 of my biggest colas are starting to show some worrying signs. I'm not sure at all what it is so I'll let you be the judge.
I also have a growlog which you can look at, but here's some basic information about my gro

Strain - 420 Carats
# of Plants - 3
Grow Type - Soil
Grow Stage - Flower
Bucket Size - 5 Gallon smartpot
Lights - Mars Hydro Reflector 192 LED panel (420W@110v; 410W@220v, PAR of 1200umol at 18 inch)
Nutrients - DutchPro Bloom (soil) A+B
Medium - BioBizz All-Mix
PPM - ~1400
PH - 6.3
RH - 60% to 65%
Room Temperature 20 to 24 celsius (68-77 fahrenheit)
Room Square Footage - 1.20m x 1.20m x 2m (3.9 feet x 3.9 feet x 6.5 feet)
Pests - None Known

Here's some pictures as well:

 

[Dwight Monk]

Looks like Bud Rot bummer , do a search here or online on it as nasty stuff and need to get rid of it (and like everything various ideas on it covering all ends of the spectrum). As I'm too new at this to have any advice/opinion on what to do, and you need to deal with it or make a decision on it.

 

[Gewber4u]

With out sought sought its bud rot. If it's just the top take cola off other wise you could end up looking the hole plant.

 

[improvise]

Ahrrr sorry to say it is the dreaded bud rot. I have had it once it has an odor that is unmistakable really nasty. Best thing to do is salvage what you can of the healthy buds and burn whats left,(drastic yes i know but the other plants will develop same if left). A note on the subject while i`am here, i did not visually see my bud rot under my l.e.d.s until i happend to take a plant out of my grow space for some reason and in normal light i instantly saw it Ahhhrrrr). Humidity plays a big part at the later flowering stage. regards

 

[GandalfGreen]

Yep you guys were right, it was bud rot all right. I cut down the parts that had any signs of it and as I was cutting them down the smell was, as improvise had suggested, truly bad. I could see the white fluff between the buds as well which was the nail in the coffin for me.
It's like a cruel joke that it happened to the biggest juiciest buds on the plant.
I checked my temperature over the last few weeks and found that it was a bit too cold. So I set up a heater which should remedy that. I also turned up the ventilation and have my monkey fan blowing over the biggest buds to prevent it from happening again.
Thank you all for the advice!