There are many different fertilizer brands out there and many of them work great. I personally started off using FoxFarm Trio of nutrients with CalMag. I used that lineup for over 6 years. I used a few others with another favorite of mine to be Blue Planet Nutrients. You can be successful with either one of those lineups so maybe see which one is available in your area and priced good.

Since you planted in a soil that already has nutrients in it, you have some time – but not a lot. What size containers are they in? The smaller container, the faster the nutrients will deplete from the soil.  Do you plan to keep in that container or transplant up to a larger container? If you transplant up to a larger container with fresh soil that has nutrients in it, then you can delay feeding bottled nutrients even longer.

Do you have a TDS tester on hand so you can check the PPM of the soil runoff? That will help give you an idea of how much nutrition is in the soil and when to feed. The PPM section of the book shows a chart with general PPM ranges for the different stages of growth. When the runoff PPM is low or about the be below the listed range, a feeding can be applied. Many growers will start with a 1/2 or 1/4 dose from what is says on the feedings chart to safe side things.