Please Help identifying leaf symptoms

[anniesron]

This is my first hydroponics grow and I need help identifying what is going on with the leaves.
The blemish on the leaves is so vague it is hard to see unless you move the light around.
The blemishes are just a duller green than the rest of the leaves.
Growing in a tub with air bubbler, using General Hydroponics nutes.
Lux = 10k (Started at 6k as a seedling and have gradually increased to current intensity)
PH = 5.9
PPM = 410
Water temp = 69
Air temp = 79
Humidity = 45

 

[TripsRabbit]

Purple petioles usually means magnesium deficiency, I would add some epsom salts to the mix.