What nutrients does my plant require

I've increase ventilation, watered using rain water and the buds have dramatically grown in size now. I have added a little bit ut of potassium and cal mag following the recent issue and she appears to be reacting OK now.

later edit - also raise Ph to 6,5.

Wow way too hot in there bro! At that temp You would need a very good CO2 station! Above 28°C tops , it´s a huge stress source. Also the lights are too close for that power. Just tweek it enough to get You throu, at this point not a lot You can do to get them fatter, but they do look good man. Keep a close eye on watering.

Also note that the pH is now 5.7...

Thanks guys, so my ec reader arrived. Run off figures are 855 at a temp of 21. 3 celcius and 402ppm

Hi Biggy2k20 if you detect overfertilization in your crop, stop applying any fertilizer and carry out a good root wash. To do this, you will only have to water the plants with clean and soft water, that is, water with a good PH. Watering abundantly, you will filter and remove the remains of substrate and salts that are concentrated in the substrate and, if everything is done properly, the plant will develop normally again. The faster you detect the excess and perform the root wash, the more chances you will have of saving the harvest.

Nitrogen firstly and then I would say cal mag and finally a shit ton of potassium. Thats should clear them up one dose of nitrogen should fix the yellowing leaves and the cal mag and pottasium will give them the boost they are needing :) Hope this helps and overall great looking grow we all run into problems at some point and im sure youll fix her right up and she will still give you a big heavy yield :) Best of luck my friend :)

An ec reader is a growers most useful tool to go along with your ph tester. Cheers

I have performed a flush and a pH test again. The pH is now 6.7 using fresh rain water. The water from the run off was almost clear, slightly yellow.

Have you checked your runoff waters values. Looks like you have overfed and the girls have locked out. Check the runoff waters ph and ec. Adjust them to proper levels for your grow type. Unfortunately when plants are overfed they will not put out the harvest that they could have. Cheers