Not sure what is happening

Auto Blueberry. This started couple days ago, First time indoor grow
Spider Farmer 2000, light - 24" above plants
Fox Farms - Grow Big, every 3 days or so
Temp - 74
Humidity - 55
The color on top leaves changed with this discoloration, any ideas of the deficiency?

This is the smaller of 2, the other looks ok. They seem small to me, but i have never grown an auto and i put the girls outside early but it was so dang hot this summer i opted to bring them inside.

@peachz; Welcome to the community. Looks like a magnesium deficency