Rust spots on my lady in puberty.

This is looking like a PH or lockout/underfeed issue to me. Potassium and something else. maybe boron by how the one leaf looks. Do you know the PH of your medium? Can test it with a slury, grab a 1/4 cup of soil. mix it with 1cup of distilled water. Switch it aorund let it sit and then measure ph of that solution. Want to grab a good sample that's lower in the pot vs top soil. Other idea is to use a TDS pen when using liquid nutrients and confirm your EC is in check and your not feeding to little or to much nutrients. Looking at your feedings, they seem like they maybe to low. but its a wild guess with out doing some math or knowing its EC. I am not overly familiar with FF nutrients. It looks like grow big hydro has your boron in it. may want some more of it. Best Of Luck!