Young seedling has a problem

[Kush]

Hi, this is my Speed Seeds Skunk Auto at day 6 from seed.
The tips of her first set of leaves are yellowing and curling up (as seen on the photo below).
Temperature in the box is rather high, could this be the problem? Or is it something else causing this?
Thanks for your help!

 

[Waira]

..most likely Kush,... seedlings are pretty tender and sensitive at this stage, and too hot puts big stress on them,... what's the T and RH cycling in there?

 

[Kush]

Temperature inside the grow box used to be 38C during light cycles, but at one point it reached 40C.
Now I managed to lower it down to 36C which is still pretty fucking hot.
Problem is that I can't do much to lower it any further. We have a frying hot summer this year and the temperature in my room is 28C. I am actually surprised that the inside of my grow box is only 8 degrees hotter than my room temperature.

 

[Kush]

I don't know if this matters, but my thermometer is not in the shade, so it measures the temperature in the direct light.


Anyway, direct light or not, 40C was too high, so here is what I did to solve the heat issue:
1. I moved the CFL lights further up and away from the seedling - a good 80 centimeters above the pot.
2. I removed the largest and hottest CFL bulb.

Now the temperature is down to 31C, but I lost a lot of light intensity. Hopefully, this won't be a problem because seedlings don't need as much light as flowering plants do. When she grows up and establishes herself, I will lower the lights once again and I will utilize the large CFL that I just removed.

If lowering the temperature doesn't cure my problem, I will have to look for other possible issues that might be causing the yellowing of the tips.

 

[Waira]

...it does, just like putting it in the direct Sun,.. it's not an accurate measure of the ambient air temp,... What soil are you in, and did you check it's pH yet?

 

[nizmoKush]

How about some silica for the heat, I just got some for my outdoor grow since it's 100°F plus (in Celsius I have no clue lol)

 

[Kush]

...it does, just like putting it in the direct Sun,.. it's not an accurate measure of the ambient air temp,... What soil are you in, and did you check it's pH yet?

Thanks for your help!
The thermometer is sitting right next to the seedling, so when it was reading 40C, this is what the seedling was getting as well. I thought that it was a very high temperature, even if the ambient temp was lower. I got scared for the life of the seedling, especially when I saw the yellowing at the tips.
The soil is 10 liters of a local East European brand for balcony flowers. I used it on my previous grow with no problems - it grew healthy plants from start to finish, so I thought that it was "OK"... I haven't checked it's pH, because I don't have a pH meter. I'm growing on a very tight budget and it is a ghetto setup (one that worked on my previous grow).

 

[Waira]

....I can understand that! well, the heat is the most likely cause anyway,... at some point, try to budget for at least a pH meter, and an Accurate 8 soil pH probe as well,... you can check pH using a meter and a specific run-off and pH calculation method, which is here in the Sticky section above this patient section,... problem is, it's a gamble to not know anything about the water and nute solution pH,.. pH is everything in soil! It's the [HASHTAG]#1[/HASHTAG] problem here in this Infirmary, troubles stemming from off pH,... it's very dynamic in the pot too, as roots and soil microbes alter pH,...as do you with your inputs; it doesn't take much drift to start getting problems,... so end of sermon! :smoking: .... heat is problematic on several levels for the plant, an can cause a cascade of problems... You're right, seedling don't want strong light like more mature plants do,... Proxomity heat is what was causing part of your issue, but you've dealt with that I see! And yes, a Si supplement is helpful for several things as well, including heat tolerance,....

 

[SouthCarolinaYardDog]

How about some silica for the heat, I just got some for my outdoor grow since it's 100°F plus (in Celsius I have no clue lol)

I'm doing first grow and decided to run sillica this time because tent gets to 84 a couple hours a day it's hot this summer I have not lost one of the 5 I started.
I believe with my own eyes how good it works!

 

[Kush]

Thanks, @Waira. I will consider buying a pH meter and a pH probe. Until then, it will be a gamble for me.
Will have to read about this silica deal as well.