Well, I had this problem with the previous Mum put into flower, with the leaves yellowing, harvested all of what was in the flower chamber, and moved the other two mums into 12/12 two (2) days ago. These plants looked GREAT!!! Schultz Liquid Plant food and Superthrive being used. After two days in 12/12 they are beginning to yellow at the new growth from the inside out (stem to tip) Veins are remaining green so far. I am using 150w HPS in a cooling hood as stated before, could the light be causing these issues, or the diff in nutrients being used by the plant, and would it effect them in this short period of time?!.....Added drip system to my bubbler that I have been having issues with and it is now the holder of two fine clones that are doing great so far. Thanks for the help on that situation. On the two that are yellowing, does it sound like Iron def?? if so would ironite be the thing to use?!

Thanks Again for the help