I've noticed this discoloration on a leaf. It has slowly got larger over time. Any idea what it is? Will it ruin my grow? I'm pretty sure its not over/under feeding because its only on this leaf. Any ideas?
It got burned from the water,
make sure you only water your soil or spray your leafs when the lights are off and will not go on for a few hours.
Overal looking at the other pictures from your diary, your plants look healthy so you are doing a good job :)
Goodluck growing
I think all it is is that you splashed some nutes/water on the leaf and it's burning from the light... I wouldn't worry about it and would actually trim it off!
Good luck!