Grow Mediums Centre of leaves going brown... Whatis!?

[YaJawstin]

Allooo! Need a little help.. Can't seem to find much Info on my problem!!!

Growing in wilma big pot with RO water and 60/40 gold



I'm little worried about the browning in the centre of the leaf... I added a little epsom salts to water 4 days ago and 2 days ago my watering timer broke and was on for <24 hours.
I am having problems with temprature at the moment but I'm not sure if the browning has anything to do with it! (Max 29deg)
This problem only seems to be on one plant and there all being treated the same!!

 

[medic grower]

Heat!!! we had a heatwave over here and i spottet the same browning in the middle of the leaf on one of my sativa girls. i can snap a pic when the lights go on later if you want...

 

[Anthropolis]

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