Advice on leaf problem (new grower)

[Xiler]

Hey folks- first time grower here. Looks like I might have a nutrient issue or something. See pics below.

Background:

White Widow feminized
Soil grow in 3gal smart pots
3 weeks into flower
Feeding every other watering with Fox Farm nutes (grow big, big bloom, tiger bloom) and feeding half the prescribed dosage.
400w HPS light

Some leaves are showing spots and there is some light green between.

Any advice would be great. Thx!

 

[BuddroGreen]

pH?

Kinda looks like Calcium def. Did you use any lime in your soil or supplement cal-mag?