Help! Plant leaf problem!

Hi all!

I have a problem with one of my plants, she's a G13 Labs PureGold approx 5 weeks into flowering.
I have been feeding every 2-3 days with Atami bloom and tomato plant food NPK 4-4-8.
I ph down the water to 6.5.
The top leaves have many dark purple/brown spots on them and mostly on the middle of the leaf.
The leaves are also curling up and feel very dry/crispy.
I am flowering under 400w HPS cooltube with temps of 72 F and fans blowing on the plant.
The other leaves on the plant are fine but it's the top leaves that have this problem.
Please see pic, sorry about quality it's my camera phone!!
Thanks

Looks kinda like nute burn, really blurry, though.

Looks like your feeding too much bro.
What type of soil are you using?

And def. DO NOT listen to TeaTreeOil. He doesn't actually grow any plants.
He just argues ...a lot.

Thanks for your reply, i'm using biobizz all-mix.
I think the plant needs a bigger pot as the roots are very compact but am unable to re-pot at this stage due to limited grow space.
Should i flush the plant next time i water?
Thanks

No worries. I would definitely recommend flushing for a couple days. Lay off the nutes until your leaves look healthier, then start slowly feeding until they respond with some healthy growth.
What size pot are you using?
Good luck!

I'm using a 10 Litre pot. It's strange that it's only the top few leaves that have this problem! Thanks

That pot should do fine for the rest of your grow.
Like I said, give it a flush then start off slowly adding nutes until she responds with some healthy growth.
Hit me up on PM if you have any other ?s. Good luck!

Hi again!
Things are getting worse today even after flushing the plant. It's the very top fan leaves they seem to have this dark blotchy pattern spreading all over it! It's on even more leaves now like in my photo. The leaves that have this are extremely dry and i think are almost dead! Can anyone help or is it too late?