Hey buddy, that definitely looks like slight overwatering to me. The way the leaves droop right after watering is a classic sign that the roots are gasping for air. In a 12L pot, 750ml is actually quite a small amount of water at once. The soil in the core is probably still moist, and with the frequent watering, no oxygen is getting in. My tip: Let the pot get really light now, until the top 2-3 cm of soil are bone dry. After that, water it well (with drainage) and then take a long break again. It'll bounce back!