Autos Yellowing at Stem

These autos are just over a month old and have been going great so far. Yesterday I noticed they are starting to develop some yellowing at the leaves on their lower stem. Should I be concerned about this and how should I fix it? I watered them a bit more yesterday and that didn’t fix it so I’m assuming it’s something to do with nutrients although autos usually don’t need many extra nutrients I thought.

You're overwatering that plant. You can tell by the algae growing on the top of the soil. You don't have to water everyday if the soil is wet. It's good to let it dry out some. You can't fix those cotyledons that are yellowing. They will shrivel up and die as will the first single bladed leaves.

Yes .... ^^^^^

cotyledons only job was to help feed the initial germed seedling , once job is finished it dies off.