Young plants has "burnt" tips.

[TheWonderer]

Hello everyone, It is my first time posting on any forum for something like this and I hope you guys can help me out.

This is also my first time trying to grow and I hope that I can finish this harvest.
I will try to explain everything first.
I created the grow box on my own. Its nothing special.

Grow box description:
L-120cm x W-120cm x D-60cm
The cooler from the bottom brings air inside, the one from the top brings the air outside, also one vent inside to get the air circulating.
Inside I have a 300W LED Full Spectrum Grow Light.

The plant, the soil, the water and the buckets
I purchased 6 seeds of Kritical Cush and I only germinated two of them in a wet paper towel for two days, everything went perfect and after two days I put them in the soil.
The soil is Canna Terra Professional Plus.
I always use water with a PH between 6 and 7 because at this moment I can not determine exactly what is the exact PH.
The buckets are regular buckets for growing any type of plants, they have 4 holes for drainage.

The plants are 14 days old since in the soil and one of them started to show some kind of disease, the very first two leaves have the tips burnt, crispy and brown. I tried to figure it out why it happened only to one of them since they are treated the same, the same light, the same water, the same soil, wind and bucket.
I found some guides online and people say that any plant can manifest different symptoms despite the environment.
So far I've never added nuts but I am planning to add nuts next week.
What do you guys think I should do now, what do you think is the actual problem, I don't think its a nute burn but despite this I flushed the sick plant today because I didn't knew what to do.

Can you guys help me with some suggestions?

[gbauto]

I'm not a soil grower but I'd say that you have signs of nute burn-the soil is amended with a nutrient mix and it's too hot for your seedlings. Hopefully, some dirt farmers will chime in with suggestions.

[Saturnalia]

I'm a dirt farmer. I'd say it looks very like nute burn. That Pro Plus soil may be too hot for the babies.
I would say that changing the soil at this stage would be too disruptive for them. Personally I would just hang on and hope they grow out of it. Be sure not to feed them.
This post is a week old. How are they now.

[pothood]

Cause: PH is Too High or Low at the Roots
Whether you're growing in soil, coco coir or in hydroponics, probably the most common reason to see yellowing and other nutrient deficiencies is the pH near the roots is too high or too low. Cannabis plants have a difficult time absorbing nutrients when the pH is off, resulting in nutrient deficiencies even if the nutrients are actually there near the roots.

Symptoms
Yellow or other oddly colored leaves
Spots, stripes or patches
Burning around the edges of leaves
In fact, basically any nutrient deficiency can be triggered by incorrect pH

How Do Growers Get It?
Growers who don't make sure their pH stays in the right range will often run into nutrient deficiencies, even if they're starting with a pure source of water and good soil!

Soil Optimum: 6-7 pH
Coco / Hydro Optimum: 5.5-6.5 pH
How to Fix

Use a kit or PH Pen to test the pH of water before you give it to your plants, and adjust if necessary by adding an acid or base to your water
Learn How to Fix Incorrect pH

[cococeltic]

I had the same with soil some soil can be a wee bit to strong for the young ones so just water for the first few times also depends on the soil try a different type next time