Having issues dont know what to do anymore

I grow in coco with medione one part line was going well until this week I noticed one plant having droopy and twisted growth and the other starting to get rust spots or something I water once a day in 3 gal fabric feed feed water with calmag. Temps about 80 lights on and 75 off humidity is low at 40 cant get it up much more just confused because they were doing great that all of a sudden I started to get these issues. Any help would be appreciated
 

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