Inexperienced grower first grow issues

Is this over watering or a nutrient toxicity?

Looks like over watering to me. I am constantly battling over watering. I thought I finally got watering down but turns out I do not. No matter what I do my plants always come out overwatered. Watering less has no effect on over watering for me, my plants are constantly over watered regardless. I Just killed 4 autos by over watering and they were given the smallest amount of water once a week. I have no idea how to water these things properly.

Either over watered or not enough light.