I have 3 leaf problems. Look at the Day 26 picture...

well well . ok you are sure about your solution tmperature on 21 degree, if yes its good. the ph in dwc should be between 5.5 and 6.5---- fluctuations in that range are ok . But your ph was much higher. and so the leaves of your plant look like. PH issues. and as you mentioned the ec was to high too. To get rid of heat, just helps a bigger tent. Those new led are very strong ( and hot) i have a similar one and i ended in gettign abiggr Tent, now my temperatures are stable on 27 degree.You may get another nutrients that are working bettr with your dwc. But alltogether , your girl dont look too bad. You know whats going wrong / keep ph in the good range, dont oerfeed/ keep the solution coll/ maybe get a bigger tent/ other nutrients. You got to eleminate the reasons for that. its the only thing that helps. Iam sure with a bigger tent, your solution is cooler and everything works bettr.