Tops starting to yellow!

Indoor grow just moved into flowering tent 4 days ago and i'm noticing the growth has slowed down and a slight yellowing on the top Canopy.
Growing in a Coco medium feeding every 4-5 days with tap water that sat out for 24 hrs mixed with 1ml Pro Tekt/.5ml Cal mag/1.5ml Foliage pro mixed in 1 gallon containers draining to waste each feeding.
400ppm going in at 5.8 coming out at 350ppm 5.5 ph runoff

Can't seem to figure out how to get this yellowing to go away any help would be great!

looks like a healthy transition into 12/12 to me. she needs more magnesium though.

Bump up your nitrogen just a tad.