Welcome to the group!
I see you have some water droplets on your Leaf. You are going to want to avoid that. Others will chime in!
What is that growing medium? Looks like mulch.
Looks maybe like a calcium deficiency.
And… I’m not sure you will be pleased having 2 plants in the same bucket. I’m not saying it won’t work, but it is definitely not ideal.
Doubt it’s a calcium deficiency. But you are going to want to stay away from miracle grow as it’s not a very MJ friendly soil. Most potting souls aren’t good for MJ, especially time release ferts
Those brown Spots are probably from water droplets acting as a magnifying glass with your light. It causes a burnt spot where the droplet is. Would recommend not allowing any water on growth as @NYDon stated.