Brown splotches on the leaves of vegging plants.

[The old dog]

https://www.thctalk.com/cannabis-foru...0&d=1493393951

Hi all,

This is my first attempt at posting a picture, so fingers crossed it works.

I have a problem with 2 plants: Heavyweight Dream Machine grown from seed. They're about 5 weeks old and have been in an Amazon for 10 days with 2 other plants, under a 600W HPS, fed on Canna Aqua Vega nutes @ the recommended 20ml per 10 litres, with cannazym, boost and rhizotonic added. Res temp is 22 degrees C and the room temp is 26. They are under a scrog screen. I use silicon to raise the PH and Growth Tech's PH down to reduce it.

I noticed these marks yesterday, but I think they've been developing unnoticed for a few days. Some of the marks look shiny (or wet) when viewed from an angle. The worst part of the leaf is brittle like overfeeding damage. Nothing has been splashed onto the leaves then 'burnt in' by the HPS. The marks vary from a light rust to pale green and there are some translucent bits too. The underside of the leaves don't look affected.

I'd welcome any ideas re this problem.

[The old dog]

I just checked out a hydro ph/nutrient table (sorry I didn't note who'd posted it) and now I'm thinking this may be a cal mag issue, since the ph keeps dropping to around 5.4 after it's been adjusted to 5.9, so calcium and magnesium are being locked out.

I use Canna Calmag to raise the local tap water from 40 to 200 TDS (500) before adding the Canna nutes etc. I also think that the ph is dropping due to the HPS being a bit close to the plants, causing them to overheat and take up more water than nutes, hence the ph drop as the res mixture loses water. I've raised the light hood (parabolic) and will monitor the ph closely.