Yellow leaves on the 3rd week - what should I do?

If you sharply increased the dose at the last feeding, do not rush to flush - first check the pH and runoff, then decide.

@green_kakha

Also check the roots - excessive watering gives the same symptom. The pot should be completely dry before watering.

@growdoc_ge

If yellowing starts from the lower row of leaves, it is often a slight nitrogen deficiency. Increase the dose slowly and check the pH.