hi grows looking for help.my loft room has failed to work many times now i am on my 8th try now useing 3 differant systems and its the same problem every time.its all wiyh young plants.after about a week or so thay start to yellow(a well watered clone in a good pot wont have been touched)it worsens slowley turning hole leaf yellow and dieing the plants hieght grows ok after a fortnight the new growth is sprouting yellow.there is good movement of air good temp light good hight but the room is may be a little dry at 35-42 rh.i have had 2 experanced growers up and still this problem. i did think it must be me so built a crude room in me garage put 4 in off thay go great guns any help or suggestions to cure this prob would be gledy recieved regardsr.