it's a little early to tell right now but sometimes yellow spotting between the veins means low magnesium. See if you're ferts have magnesium in them. I don't use those, so I don't know. Also, since you say it's at three feet, you might consider going to a 12/12 light cycle now, as it will keep growing in flower. All depends on how tall you want that plant to be. At three feet it might be starting to outgrow its 4 gallon pot too. You might consider transplanting to a larger tub. 4 gallon will probably work but it's going to get tight in there. If a few days go by and the yellow spotting gets worse and it looks like early mg deficiency, you can probably solve it just fine with a level teaspoon of epsom salt in a gallon of water next time you water. Also, you need to let the soil dry out some before feeding. Otherwise, looks good to me.