almost glowing leaf blade

Good day peoples. Thanks for checking this out. I usually can come up with a hypothesis, right or wrong, but this is new to me...

Just a blade or two on one leaf, at the top of a few plants is very bright and completely yellow. Almost fluorescent yellow.
more info: http://boards.cannabis.com/grow-log/...t-success.html


coco
Drip 2xday
E-indoor
E-canna coco w/ higromite in a one inch layer on bottom
SCLR-Soil or slab runoff pH----6.0 ph
E-Water source------R/O
E-Source water pH-----8.0 corrected to 6.0 before feeding
HRT-Source water EC (if hydro)-----20 ppms
E-Age of plant---5 weeks from seed
E-Botanicare Grow, Cal-mag, Liquid Karma
E-Rate of application (if hydro,)---250-300 Calmag, 400 Grow, 150-200 Karma
E-Lighting source and distance from plant---Just switched 2 days ago from Fluoro's to 4x400 MH. They are about 2 ft away. Started them off 3ft. away
E-Air temperature----75 daytime, 85 night...my heater has been acting up.
HD-Reservoir temperature...not sure, but probably around 60+ degrees
E= 45-55% day, 70-80% night. Put in a dehumidifier today.
E-Lighting schedule---16/8
E-Type of ventilation your room has---6 inch intake, 6 inch outake both on fan speed controllers to insure some negative pressure
TR-Did you pre-soak your media in pH corrected solution?