If your plants are big enough that they need a transplant (5 nodes), they are ready to fert.
Or you could watch for N def to set in, and let your plants tell you when they are hungry... but that's not optimal. Since you did this once before, you know that week 3 they are hungry, so start a 1/2 strength feed halfway through week 2 and watch for any sign of burn.
Feed-feed-feed-flush or something is a fine schedule... the flush step, if your plants are looking healthy, doesn't have to be a crazyu full flush, just plain water until it runs out the holes. I think all dirt growers do it differently, lol... your plants will tell you what they want. Listen to them.