Small Slices on Seedlings main stem

Hello RIU, I am near the start of my first autoflower grow and the seedlings are just 13 days (Day 1 being when they popped from soil) I check on these babies a couple times a day. I noticed a couple days ago that one of my plants had a small slice on the side of the main stem, almost like it was cut with a razor blade. I thought it was strange but not a huge deal because the plant is rapidly growing on a daily basis with zero signs of over watering, under watering or nut diff. I am a bit concerned now that I have seen the same type of little cuts on my other seedling today. There is zero way wild life can come in my grow box so I have ruled that out.

A bit of info on my set up:

Grow box: roughly, 3ftX6ftX3ft Covered in Reflective Mylar and air tight with just two intake fans and one exhaust fan

Lights: 75 actual Watts worth of LED ( 300 Red:blue 4:1) and twenty 23 watt CFL's

Soil Based Medium: Fox Farms Ocean Forest and perlite, 50-50 blend, except the inch or two of pure perlite at the base of my 5 Gallon smart pots and a 1 inch perlite layer at the top of the pot, (base of the plants growth) to keep out any fungus gnats and all those bastards.

I water when I know they need water because I like my plants to search for that moisture and expand their root structure at an early age.

Imgur is down so I had to use tiny pic I hope the photo turns out and is helpful
[/IMG]

I guess it didnt work here you are, you can kinda see the little cut on the side more towards the base too. It is just the skin of the stem and I have never seen this and have no idea what it is anyone have any input? again it is not a deep flesh wound it looks like the skin is torn slightly.

I forgot to add my RH was around 30% (for the first week only) until I got my humidifier that I have been using for the last few days before the tear was even visible. My RH is now a constant 50-60+% depending on the time of the day (having some heat waves here in Southern California.

ya, that might have been an RH issue, it makes sense that if it was too dry the outer stem might have gotten too stiff to account for the rapid growth. now that you have the rh under control see if it continues.

I had made sure to mist more often and I tried to feed the leaves twice a day to prevent that but you probably are right. It did get to the lowers 20s when it was over 100 this past weekend so you might be right.

My only other concern would be why did the other one do it after the RH was fine for the past 3 or 4 days. The plant might have made a slight tear and i just didnt notice it until it grew bigger and the slice got a little better. I am going to give it a couple days then do you think a thin piece of athletic tape would be needed to cover the wound from infections and all that? maybe even a bandage, ha.

and I should specify it was over 100 outside, my box never gets over 88 and it usually sits at about 75-80 most the time .

ya you can use tape for a week, thats what i do if i split it doing supercropping.

Again thanks for the input Man, this is such a weird occurrence!

It was just the baby skin falling off I guess. Usually it comes off from the top down but this time it just split like a cut and I think it was because of the dryness and the stalk wasnt ready to get rid of the skin yet. I laughed at myself after realizing that it was nothing...I am in hopes the admins delete this thread..

nothing to worry about im sure

yes they are doing great, I was a bit rough on the LST and I think that made them slow down a bit but they seem to be right on schedule. They are autos I probably should have just trained it a bit and made more light for the bud sites because the Auxin change really slowed down the verticle growth up until a few days ago. Next time they get that L-Lst