First signs of nut burn?

[Singed]

I just started these two plants about a week and a half ago when i bought the clones from the clinic. Ive noticed the leaves on the sides have a slight lighter color to them, and i'm uncertain whether or not i should be worried.

The other 4 plans are ones that i picked up on saturday. I'm growing hydropnically with a homemade ebb and flo set up. The 2 in the back are white widow, the two in the middle are purple kush, the one of the bottom left is OG kush, and the one on the bottom right is purple elephant.

Let me know what you think. Thank you everyone

Oh im using FloroGro, Bloom, Micro, and also flouracious plus for my nutrients.

Ive got a 31 gallon res and i probably fill it up to about 20-23 gallons full. I put in the nuts required for 15 gallons which someone at the hydro store told me to do. I currently dont have a PPM measure, but i top off my water every night and make sure the PH is 6.

Attachment 285543 pe

Attachment 285544 og

Attachment 285545

ask any questions you like, and please let me know what you think.
Thank you