Silver Spots, ends look a litlle burnt have pics

This little one has been through a lot in the past, but just when i think i finally got it something else pops up. Now i am getting silver spots on some of the new leaves and slight burning on the sides.

She is in a grow room where the temp never goes over 80 degrees. She is in COCO medium, feeding half strength COCO nutes part A and B. Getting 900-1000 LMS via 400 W HPS on 18-6. Temp is kept down via fans and air con. watering every 3 or so days.

Does this sort of problem happen with under nuting?

Looks like a deficiency for sure. Iron possibly from PH being way off. What is your PH of water you put in and water that runs off?

your pH needs to be 5.5 and you need to up your nutes, they should be dark green... Coco needs to be watered every day when young and every other day once it's established

Thanks! I have been setting pH to 5.8.. will try 5.5 from now.

So if they start turning lighter green thats a good sign its time to up the nutes... ill look out for that in the future

5.8 should be fine really, but you do need to seriously up the nutes and increase the waterings