Hard to see, hoping I caught it soon enough but not to soon.

[Douche_Bigalow]

Hello and good day to everyone.
I have 5 Ladies in a uc6 (8 gallon)
3000 watts
Chiller
Co2:1200-1250.
PPM:650
PH: 5.79
R.O. water
Lux reading at the highest Cola: 90.
Water Temp: 62-67
Relative humidity:65-70% daytime. 30-45 night time.
Temp: 26-30

I noticed this browning spots on the cola. I have recently changed the water out as normal and am using heavy 16 only. Third week of flower.

It is a little harder to see in the picture. I will get a pick with light off later. I have my ideas as to what it is but I am uncertain and I do not want to taint the hivemind's diagnosis with my laymen thoughts. I had a really bad case of what I thought was root rot but have learned that it was "brown algae". I have been told that it is almost always a crop killer in RDWC. I spanked that stuff like it was a $50 hooker at mardi gras that has gone 3 days without a rock. Everything else is going well. Just these browning spots on the top part of the fan leaves about the flower.

Any help in identifying this so I can spank it as well would be awesome.

Alright, adding pics as I promised.
See the thing I am talking about?

Here is what the one next to it looks like.

And here is a side shot of what both of them look like.

I hope this helps someone identify what this is.

 

[bulldog74]

I notice you are hitting around week 3 of flower. Are you using CALMAG? What strain?

 

[mango420]

What rates are you feeding the heavy 16? Are you using both parts? How close is the light to the top? IMO it looks like either a boron deficiency or light burn.

 

[Douche_Bigalow]

I notice you are hitting around week 3 of flower. Are you using CALMAG? What strain?

Yes, I am using Epsom salt for the cal mag. I was told it is Raspberry when I got the clones.

EDIT: I am just adding a little bit of the CALMAG in salt form. Is there an amount that you would recommend me to add or is there something that I should be looking for on the plant to show a deficiency?
Thanks for stopping by I really need the help.

 

[Douche_Bigalow]

What rates are you feeding the heavy 16? Are you using both parts? How close is the light to the top? IMO it looks like either a boron deficiency or light burn.

I am not doing a per gallon dose measurement on the nutes. I called and chatted with the dude that makes the stuff and he talked me though what he advises for the feeding. Basically, after a dump and fill I use the RO water and I add equal parts a+b starting at 200ml so 200 a + 200 b and then wait an hour measure the PPM and then do the math to see how much more I need to add to get the ppm's that I want. At the moment I get to the 750-800 range and as long as the ph is at or below 5.8 but not below 5.2. At this point I consider this my starting point. I am carrying my water in from a machine that is 1.25$ for 5 gallons. I should be getting an RO machine this week though and when that happens I will start stacking. Meaning that I will not do a complete change of the water unless I am changing from veg to flower or get any issues that I need to treat. Like the Brown algae I had a bit ago. The Ro machine will be on a float valve and auto top off the system. Then once a week on the same day. I will top off the nutes.

Currently the lights are 18-24 inches away from the top of the plant's. Currently I am getting about 75 lux on the highest cola. This translates to 6.967728 or about 7 lm/ft2. This is at the highest cola.
I also was thinking it could be a boron deficiency but after looking at the remainder of the plants this is the only location that this type of markings/damage is showing. This is my first grow so I have no first hand experiences with Boron or the lack there of. I think the light burn idea may be spot on. After I noticed it I raised the lights 6 inches and I have not had any addition to the area or new locations appear anywhere else.

After all of this info do you read anything that I may be doing wrong? Also, thank you for stopping by.