whitish yellow leaves, purple buds (pics)

I got these almost white leaves at the tops of my plant. Im not exactly sure what caused it so I thought I would ask.

This problem started as soon as i switched to 12/12 and stoped after about 2-3 weeks.
I think it was caused by either light burn/ bleaching or a nutrient deficiency, I had high temps going into flowering that I had to get under control, and I was also giving the plant a pretty weak ppm (unknowingly). I fixed both problems within two weeks and the plant was back on track.

Plant info
400w hps
6 weeks flower
bag seed
1 plant lst
dwc
vegged 11 weeks under 150w hps

Just want to be sure about what it was that caused the leaves to turn whiteish.
What does everybody think?

Also this is my first grow. Thanks for the help!

its a defiancy of some sort and the purp is prob just the strain it should be fine though how long are u gonna flower for and i noticed u did some lst u should check out my thread below its pretty cool

mcpurple said:

its a defiancy of some sort and the purp is prob just the strain it should be fine though how long are u gonna flower for and i noticed u did some lst u should check out my thread below its pretty cool

Click to expand...

I was just reading some of your thread yesterday! lol
Ive learned alot about lst from this grow so far and know what major improvments Im making on my next one im working on right now.
Im going to flower for 10 weeks probably but I plan on cutting a branch or two at 8 weeks beause Im going on vacation. Im only leaving for 5 days, you think my plants will be alright while flushing without me?

Looks like either Iron of Nitrogen def. I hate to link off site but I don't know where the proper thread is here on RIU, but check this out, it has helped me many times.

http://www.icmag.com/ic/showthread.php?t=11688&page=1

Conrad101 said:

Looks like either Iron of Nitrogen def. I hate to link off site but I don't know where the proper thread is here on RIU, but check this out, it has helped me many times.

http://www.icmag.com/ic/showthread.php?t=11688&page=1

Click to expand...

NICE! this is an awsome guide! I read through it and now think the problem was a sulfur deficiency that was possibly aggravated by high temps. Thanks alot! + rep

Cannabis Smoke said:

I was just reading some of your thread yesterday! lol
Ive learned alot about lst from this grow so far and know what major improvments Im making on my next one im working on right now.
Im going to flower for 10 weeks probably but I plan on cutting a branch or two at 8 weeks beause Im going on vacation. Im only leaving for 5 days, you think my plants will be alright while flushing without me?

Click to expand...

oh cool you found it before i even told u. and they should be fine flushing with out you. and when u flush the leafs will turn more yellow but thats normal cuz u flush all the nutes out so dont be worried if it gets worse when u flush.