Plant dying!

Alright i can't put up pics yet by i'll do that soon enough but just a shot in the dark.... My plant is about 4-5 weeks into flowering and at first the top leads were a pale green then they strted to turn yellow then the rest of the plant slowly followed turning from a healthy green, then pale. A lot of the leaves are even yellow and burnt looking on the ends as well as down the middle. I'm using FF ocean forest soil with big bloom FF nutes... I suspected that maybe i was over-nuting so i flushed the soil with a whole heck of a lot of plain water and now i'm letting the soil dry out... but the whole plant is looking pretty pathetic and close to death...it's yellowing terribly. What the hell do i do?! Any suggestions would be greatly appreciated..!!!

Additional info: I'm using a 400 watt HPS

I have some older pics i took with an iphone that i'll post but keep in mind, the problem is much worse now..

see if you can get a hold of superthrive put like 3 drops into a half gallon and water it with that its awsome man like vitamin b for us but for plants

it is natural for some fan leaves to turn yellow during flowering because bloom fertilizers are low on nitrogen. but at 5 weeks flower having the whole plant turn yellow sounds like you had a nitrogen deficiency for the whole grow. also, check your pH to make sure you're not getting nute lock out