Easily the most common reason growers will see an iron deficiency is if the pH at the roots is too high. Iron tends to get locked at at higher pH levels, especially when the pH is above 7.0, and iron deficiencies are more commonly seen in soil or coco coir than in hydro.
If you suspect your growing cannabis plant has a iron deficiency due to too-high pH, flush your system with clean, pH'd water. This will remove any nutrient salts that may be affecting the uptake of iron and help restore pH to the proper levels..
In soil, iron is best absorbed by the roots in the 6.0 - 6.5 pH range (although it's generally recommended for soil growers to keep pH in the 6.0-7.0 range, iron tends to get locked out when the pH is higher, especially above 7.0)
In coco coir or hydro, iron is best absorbed by the roots in the 5.5 - 6.5 pH range
It looks like your plant is giving you a high five . high five it back, flush it throughly and ph your water and carry on and be sure to keep your temps optimal and air flow and all should be good homie,
Leaves and plant look amazing keep it up, all the best,
I also agree ruling out heat as a problem, I never ph'd in soil and had this happen so yeah definitely a ph problem.
Love2grow28 over and out!
"You can go into any drugstore in any city in the nation and you'll find any drug you want, and they will be more addictive and worse for you than cannabis, "Woody Harrelson"
Hi all thanks for your help, I didn’t realise everyone was commenting on this I haven’t been back on here for a while so I apologise for not replying. After a bit of experimenting I worked out it was heat stress my room was getting far too hot the highest temp recorded was 32C I bought a cheap fan controller and a thermostatic tube heater for 30 quid and now she is back to perfect health and ready to be used as clone stock