Weird leaves stains

so the shape of that brown part of the leaf kinda looks like it may have been splashed with water which then magnified your light and burned the leaf. it doesn't look like any sort of deficiency. I can't tell exactly what kind of lighting you have, but some of your earlier pics show some purple lighting. if your light is too close it can easily cause burn marks where water is sitting on the leaves. how close to put the light is determined by how strong it is and the type of lighting. most of the time you want the light at a minimum of 12in(30cm) from the plants unless it is a really weak light. so maybe back off on the light a little and be more careful when watering so you don't splash on the plants leaves.