Centre of bud leaves growing out yellow

So I have 3 plants growing of unknown strain (I was given them as clones but don't know anymore info).
I have them in 8.5 litre pots under 1500w hps light.
I feed them about every 2 days about 1.5 litres each with about 6mls of a hydro A and B nutrients (we were going to do hydro but ended up getting soil potted clones).
They are just about at week 4 of flower and have been growing well up till now.
One plant haspecies now started to sprout yellow leaves at the top of one bud they start out yellow but thenot the ends turn green. They were a bit close to the lights so have moved it up and added a better fan to keep template down. I haven't been able to find anything that looks exactly the same,the closest I could find pointed to iron deficiency. I have been feeding it just water for the last few days and any help would be great. The rest of the bus seem to be ok.
Here's a couple pics.

1500 watt light is a strong light and it likely has hot spots
youll want to keep it like 30 to 36" above the canopy

so it could be light bleaching... if its the only plant showing the issue and it happened to be close to the light id have to go with that

if its not light bleaching then yes id have to say you've got an iron issue or a ph issue
but honestly I think its light bleaching

how much % of iron is listed in each of the hydro a&b

I'll have to check the bottles. But I think you are right with the light bleaching, it's the only one to have it and I think it was too hot too as I think it's fox tailing too and it's not growing right. I have raise the light as high as it can go and added a more powerful fan to keep the tops cooler. Can I remove the affected tips without to much issues?

I would remove them
just let them be

put that plant in the corner furthest from the light

use stakes or string and tie/bend the tops down away from the light

carefully not to break

loop the string at the bottom of the main stem

gently and slowly wrap the string up around the stalk to close to or a couple inches from the top

use the string to bend the top downward without snapping the stem and tie it to something heavy enough to hold it down

even 4" makes a big difference!

http://rollitup.org/t/lets-get-dirty.937239/

page 1 shows how I do mine

but since your in flower I wouldn't go as extreme as I did

just take out some of the height directly under the lamp

post #4 and post #13 pics

same plant

Thanks for help. Will see how it goes

if your plants have super thick stalks and they wont bend then it wont work for you... don't snap them

it just depends on the type of plant