By continuing to use the website or clicking Accept you consent to our cookies and personal data policy and confirm that you are at least 18 year old. For details please see Privacy Policy and Terms
Could be really bad light stress...
My guess would be that a high PK nute has locked out calmag and other micronutrients. If you're using a booster, roll it back a bit.
As always, check your pH and EC going in and coming out.