A little yellow, opinions on which way to go...pics

Alright, the lower leaves on my plant are yellowing. I know this can be from a number of things.
About my Grow...
Nutes: I have been feeding with foxfarm grow big and just started adding big bloom. I feed with every watering at normal strength(1 tbsp per gal).
Water: I water about once a week, and I use my finger to tell when soil is dry about 2" deep.
Temp: My temp had been getting into the upper 80's with my hps on, so I took it down and am back with my cfls. The temp is now in the mid to low 80's during the day and low 70s at night.
pH: The pH of my water was around 6.5-7 after I added nutrients, so I lowered it back to 6, which is what I normally use.

The only thing I can think of would be nute lock up? Any help is appreciated!
Pics:

The tips of the leaves are also a little brown

You can see the yellow beginning to work its way up in the different tones of the leaves.

I'm no expert, but this has happened to my plant before. From these pictures it seems like these leaves are no longer taking in enough light to be beneficial to the plant because they are blocked by the leaves above. The plant figures it shouldn't be feeding leaves that aren't contributing to the growth of the plant so it kills them. I could be wrong but just trying to help

thegtiguy said:

Alright, the lower leaves on my plant are yellowing. I know this can be from a number of things.
About my Grow...
Nutes: I have been feeding with foxfarm grow big and just started adding big bloom. I feed with every watering at normal strength(1 tbsp per gal).
Water: I water about once a week, and I use my finger to tell when soil is dry about 2" deep.
Temp: My temp had been getting into the upper 80's with my hps on, so I took it down and am back with my cfls. The temp is now in the mid to low 80's during the day and low 70s at night.
pH: The pH of my water was around 6.5-7 after I added nutrients, so I lowered it back to 6, which is what I normally use.

The only thing I can think of would be nute lock up? Any help is appreciated!
Pics:

The tips of the leaves are also a little brown

You can see the yellow beginning to work its way up in the different tones of the leaves.

Click to expand...

i'd probably agree with silverhaze. can you do a top down pic? does new growth from the top have any yellowing?

you may just need to flush the soil, if it's a nute/salt build up.

Here is a top down pic from yesterday when I had the hps in. No yellowing on the new growth. It is quite the bush.

SilverHaze917 said:

I'm no expert, but this has happened to my plant before. From these pictures it seems like these leaves are no longer taking in enough light to be beneficial to the plant because they are blocked by the leaves above. The plant figures it shouldn't be feeding leaves that aren't contributing to the growth of the plant so it kills them. I could be wrong but just trying to help

Click to expand...

Exactamondo and spot on my friend, first post too, so Welcome to RIU.

thegtiguy said:

Here is a top down pic from yesterday when I had the hps in. No yellowing on the new growth. It is quite the bush.

Click to expand...

yeah that looks fine my friend. all the best.

Well, it has gotten progressively worse. I flushed last night and I am hoping that will help. Here are some pics if anyone can help diagnose...

thegtiguy said:

Well, it has gotten progressively worse. I flushed last night and I am hoping that will help. Here are some pics if anyone can help diagnose...

Click to expand...

yeah that has got worse. are you using just plain soil? ie no perlite or similar mixed in.

Yes, just soil. No other medium. The plant also has obvious heat stress, ie. the curled down leaves in the first pic.

thegtiguy said:

Yes, just soil. No other medium. The plant also has obvious heat stress, ie. the curled down leaves in the first pic.

Click to expand...

your only using cfl's tho yeah? how is your ventilation?