Howdy. You might ask yourself, did I underfeed or overfeed and it may be a little more nuanced than that. Here's a scenario... You go light on your feed but then wind up being short on the volume of water you were using when you watered. Even though the plant is fed light, the salt concentration accumulates in the soil and now the plant is feeding off of salt EC of an unknown nutritious composition. What this gives you is a full combination of "painted nails" suggesting its overfed, pale leaves where its underfed, and yellow leaves where the plant is having calcium and potassium competing for the same cation points because of root stress. As you're smoking some of that weed after harvest and thinking about your next run, think about offering a steady but light delivery of nutrients to the plant, and enough volume of water poured through the medium to move junk out and good in.
Harvest signaling, keep an eye on the hairs first and when they turn from white to orange or brown and there aren't any more fresh white ones coming in, you can begin looking up close under magnification at the trichomes. They are like clear dew drops when they're immature. When most of them appear cloudy or dirty you are in the harvest window.
Another thing that's good to know is the nutrient demand curve so that you're delivering what the plant needs when it needs it but also not wasting your nutrients when it doesn't. I'm going to guess you're roughly around week 5-6 and if so, next week you'll be coming up on peak demand window so they should get their heaviest feed the entire grow, but don't let the root environment climb above 2.5 EC. Best of luck and enjoy smoking that thing in about another month and a half or so.