Yellowing leaves

Looks like N deficiency. Watering = wet / dry cycle. allow 1" to dry before watering thoroughly and fully with 10-20% runoff. This helps reduce buildup of unused ferts in medium. if oyu haven't been doing that, try that first before adding anything, even though this really does look like N tdeficiency. Also, consider recent behaviour. if you haven't fed at all, you can safely feed, for example, as the soil is likely running out of initial nutes. If in soil, make sure you feed and irrigate somehwere near 6.5-6.8 pH most problems occur due to doing too much or an imbalance of nutes or pH. so, just consider your recent behaviour if you choose to go a more proactive route.