Have i overwatered?

Overwatered. its less about the volume it needs and how much it can hold. You will find their are amounts it can hold from bone dry to soaking wet, that will all depend on the medium as well. When I water its best to use the weight method and realize not all plants drink the same. So 3L one week might be ok but it's not ok the next and maybe not for all the plants. I try and gauge my plants weight by picking it up and guessing out much it needs. So far so good and no overwatering issues this run.

Wait and lift pots, if plant is playing up, top soil can be dry, but bottoms not used. Thats how you get overwatering. Dont let plants stand in run off, better always use gravity and some plant trays/trollies, collect run off. Maybe its just photo, but it looks like first symptoms of Magnesium too, keep an eye.