Leaves slightly yellowing/browning

Can anyone help me figure out what might have caused this? I have a full description of the grow in a grow journal but basically this is day 20 of a fastbuds Girl scout cookies autoflower in fox farms ocean forest w/ perlite. 20/4 light cycle with 300w LED that was at about 20" but was moved to 25" this morning because I noticed a little red on the stems. I've used no nutrients and just used tap water with the pH as close to 6 as I can get it for watering. They were just watered last night and I just noticed the yellowing this morning. This is my very first grow so I'm not entirely sure what this issue is or what causes it. Thank you guys!

This is completely normal to happen at this stage. The first set of leaves will die off, this is not a sign of deficiency. Now if you see discoloration in the newer growth that’s when you may have problems. Looks great!

Grow So High said:

This is completely normal to happen at this stage. The first set of leaves will die off, this is not a sign of deficiency. Now if you see discoloration in the newer growth that’s when you may have problems. Looks great!

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Okay awesome, and thank you I appreciate it!