Looks like your pH might be a little wonky man. 3 fingered leaves + yellowing + possible cal/mag deficiency points me to that conclusion. Maybe she is a little hungry for some nitrogen depending on your soil and watering frequency.
In my opinion those brown spots look like an early stage cal/mag deficiency. Light stress or burn turns your leaves tips and edges white first, then the leaf dies. If you Google light burn cannabis, you will see it looks really distinctive.
Best of luck on the grow. I love space buckets.
-G
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