Rollitup pretty much nailed it. You didn't say what you were using for a root mat if anything. Are you using rockwool slabs coco fiber? You are definatley locked up. Your stems are really purple and the plants look really stressed. Looks like they aren't taking in water. I would have backed off on the cal/mag, lowered my ppm to 400-450 and decreased the watering duration to allow your medium to dry out a bit if your using something that retains water. I would PH to 5.9 to give a buffer on either side to handle any swings.My gut feeling is that either your PH is off due to temps and your root zone is too wet. I could be full of shit though because there are too many variables that I don't know.Running aero/nft/hydro it is super critical to keep your solution cool. If you dip your finger in the solution and it feels comfortable to you it is too warm for the plants. Take into account the solution has to travel through black hose that has a lot of surface area exposed to the temps in your room. If your solution is 75 degrees in the res it may come out at 80 degrees at the sprayer. I always shot for mid to high 60's in the res. When you touch the solution it should feel cool. This applies to any nutrient regimen you choose.In a set up like yours take into account that there is no medium to use as a buffer. Your roots are exposed to fresh solution all the time so temp and PH are super critical. With Lucas in your system I doubt you would ever need to see a ppm over 800 but this depends on the strain also. Overall I would say that switching strains and feeding style set you up for failure. I would have stuck with the Hindu and run Lucas because you are familiar with the plant and how it behaves. Don't be afraid to use tap water also. I have run Lucas with well water as high as 200 ppm and city water at 70 without any ill effects. Just some minor adjustments to the strength of my solution.Always remember to start slow and build up. It's better to under feed than over feed. When your plants bounce back play with your feeding cycle. Increase your off time until you see your plants droop just a touch so you know exactly what you max/min times are. This is very important in your system to get it dialed in. Don't give up brother because when you get it figured out you will have that Ah-haa moment and it will make you a more confident grower because you overcame the challenge. You have a tough system to grow with but stick with it!Be well..