It’s a Calcium deficiency. There’s many reasons for a Calcium deficiency.
An excessive amount of ammonium, potassium, magnesium and/or sodium in the root environment. The absorption is curbed mostly by ammonium and least by sodium.
Problems with the evaporation caused by an excessively high EC value or by excessively high or low relative humidity.
In soil, using tap water, a proper Calcium deficiency is extremely rare, there’s plenty enough in both of them.