Hi WashougalWonder
Thanks for your reply. Just checked my iast 24hrs min and max temps, 8degC and 20degC which equates to 46degF and 68degF. Checked my hydro temp (daytime) which is 21degC or 70degF will get up early to check night time temp but I guess it will be much lower...
If the fluid temp is kept fairly constant (perhaps with an aquarium heater?) is the air temp less critical?
The reason I ask is the plant nearest the intake duct has leaves which curl down and also has some yellow/gold speckles whereas the other is looking really well. I want to understand why this is happening to only one plant. pH is constant at 5.8, EC is 0.7, both plants fed with canna-start at a mix of 1:250 (4ml/l) as recommended on bottle, fluid level approx 10mm below baskets. 16 days old Kaya47 grown from seed in root-rite cubes supported with geolite expanded clay balls.

Being new to indoor gardening, I have so much to learn...

I have attached some pics. Note, healthy one is showing slight twist which was fine yesterday. Also purple stems on both which I'm guessing is due to temps rather than nutrients?
Sorry about photo colour - the lights are on!