Yellow leaf centers on 5 week old seedlings

[thekid818]

I popped some seeds 5 weeks ago. They are getting yellow centers. I took them off their nutes and have them on tap water for the next 24 hours before I mix up this week's food. Let me know if you guys have any ideas on what I am doing wrong. I have grown clones before but not seeds.

Growroom: 8x8 room
Light: 400W MH on 18/6 photoperiod
Temp: Daytime 78 deg. / night 78 deg.
RH: 70%
Plants: OG Kush x Chemdog seeds
Age: 5 weeks seedings
Hydro: 4x4 flood tray with 2 gallon pots
Nutes: Advanced Nutrients Sensi A/B no additives other than phdown
Water: RO
PH: 5.6
PPM: 600

 

[BrotherMonk]

How close are your lights?

 

[lysol]

Looks like heat, is that 78f at canopy level?

 

[thekid818]

Thanks for the info. Heat & closeness of the light were something I wasn't even considering. But my perlite is a little crispy in some places so do you think that means heat? I will move the light. Thank you all.

 

[lysol]

Thanks for the info. Heat & closeness of the light were something I wasn't even considering. But my perlite is a little crispy in some places so do you think that means heat? I will move the light. Thank you all.

Not neccessarily, perlite will dry out either way