please help, not sure of deficiency

hi all, hope you peeps can help, I know it's a deficiency of some sort, but not sure if iron,mag,calc etc.

I'm using ionic bloom fert with ionic boost.
room temps are (dark) 16deg (lights on) 21deg
humid between 50 and 70.
ph at 5.7
ec at 2.0

plants are 2 weeks into flower. using dwc. strain is matanuska tundra.

someone please take a look at the pics, I'm stumped

Roots are browning and plant is dying, get some peroxide at 17.5% grade min and add every 4 days diluted.

Another thing thats too cold 21, get it up to 24 at least.

*BUDS said:

Roots are browning and plant is dying, get some peroxide at 17.5% grade min and add every 4 days diluted.

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I've checked the roots they are fine, sry should have said been using h2o every couple of days. You think that cold could cause a problem, this strain is from an alaska vallay it rarely gets above 21deg even during the warmest summer. I'd expect it in a sub tropic strain but not this one. I've kinda kept the temps at the same range as the original strain would grow in.

Any other ideas, I'm scratching my head here.

Might also mention I'm growing under 4 *300w led lights (the latest type with 7 bands) not sure if that would make any difference.

From what I've looked at in the plant abuse pics it resembles an iron deficiency, but I'd be surprised at this as the ph has always been within 5.5 and 6.1 so never too high.

It seems to affect the new growth, starting at the top of the plant but has now since yesterday spread to the new grow tips further down the plant. I noticed it last weekend forming at the tops, so did a complete flush on monday. Then set it all up with fresh water and nutes. But it's not kept it in check, if anything it's got worse.

No it just slows the growth. Well how about checking that ph and have it on 5.8 with a new meter or calibrate the one you got..

I'll try another meter, the one i have is new and calibrated, but ya never know could be faulty. will do it tomorrow and post back then. cheers.

At the minute I'm foilar feeding with a half strength solution, bit of a plaster over it but all i can do until i nail the cause down.

ok checked the ph meter, well didn't check it went and got another for comparison, both are reading 5.8ph and both calibrated with ph7 buffer. So hopefully that rules out a ph imbalance. What do you think could this be a sulphur deficiency? Maybe need a bit of epsom salts.....any thoughts people?

should mention that the yellowing is most prolific in the grow tips, on the larger older fan leaves it spreads from where the stem attaches and then outward, best view of this is in pic #6 above (the larger leaf toward the bottom of the pic).

Just checked the ppm of the tap water I'm using, ph comes in at 7 to 7.2 and ppm 250 ( a little high ppm but ph neutral).