Ah, Fox Farm OC. Talked to someone else about this today, actually.
Ocean Forest is highly amended, especially w/ Nitrogen and why they advertise that it can take your plant through the entire 'early veg' stage without adding nutrients. When I used OC I followed what others have recommended on this thread about waiting for 3-4 true fan leave sets (usually after seeding stage, 2-3 weeks into Veg). What I will add is that OC is tough to gauge when it comes to adding Nitrogen and can burn quite easily. I highly suggest starting a little lower with your nitrogen supplementation, then your manufacturers nutrient schedule suggests (to start), while maintaining the recommended doses of P/K and Cal/mag. If your girl doesn't react negatively to the initial feeds, slowly bump up Nitrogen from here on out.
OC is a hard medium to gauge and when to start full dose nutrients can be a hard decision to make. The old saying, "start low, go slow" comes to mind. Simply test over time what she wants/needs and when she/wants needs it (NPK and micro nutrients). Personal example with my first grow: Started feeding full dose early veg nutrients in week 3, as recommended, while using Ocean Forest. These doses were low, the plant had adequate foliar surface area, root system and node points. They burned....lol. OC Nitrogen and my nutrients compounded and caused an immediate and obvious nute burn on the girls. For the next 2 or 3 feeds I cut my main Nitrogen supplementation by half or outed it completely, while maintaining the rest of the recommended feed schedule. By week 4-5 I noticed a slight Nitrogen deficiency which told me the plant had taken the available Nitrogen from the soil and I now needed to add it in with my feeds. Unfortunately but realistically this will be a personal trial and error period to see how OC works for you and how your feeds will react to the amended soil.
Hope I didn't go on too long and I hope this helped, without making anything more confusing. Cheers and happy grows my friend! You're on your way👍