3 week old leaves are curling up and the tips of the leaves are turning yellow.

These are a little over 3 week old plants.
I have them in a grow tent. They have been doing really good and then all of a sudden after I transplanted them they started to crisp and then the tips are turning yellow.
The light is all the way at the top at the grow tent and I haven’t changed anything so I have no idea on what happened.
Any ideas?
 

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I used 707 soil. It’s around 75 degrees inside. The light I have it running for 18 hours and then off for 6hrs. I haven’t fed them anything yet. The humidity is around 55%.
 
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