low humidity won't do that...changing from led to hps can mess with them until they get used to it but it looks more like overnute or heat stress to me
yeah don't put them outside there dying from lack of water/ sun..its no good spraying the soil unless your spraying alot...plsnts need to harden up before going outside...in future keep them indoors and water at least 50ml for a party cup
yeah you have some deficiency issues probably from the medium your using...its hard to say exactly what and why without knowing everything but definite cal mag issues...
you'll find that high humidity won't bother most strains you just have to be careful from mold.i have a basement grow that's always 90 plus humidity and they grow fine.try a bigger extraction fan if you can
they look fine to me, a bit out of whack because of what youve done but otherwise ok,go back to your feed schedule and try not to let every little dodgy leaf make you panic into killing them by trying to help.