Have you fed them anything?
Id lean it looks a bit N toxic, but happy frog out the bag doesnt usually burn plants this much.
Cant be phosphorus deficient as there isnt much need for it at this stage.
How far and what kind of lights do you use?
Where is your water from?
And what are your temps/humidity looking like?
It’s almost like it’s a extremely hot soil but I haven’t had happy frog do that before
What kind of light and what height do you have it also looks like it was to close to the light can see the leaves praying to the light but of course it could be something different
I think this is an important question.