Hi Elisabeth, sorry to see you're having problems.
It seems like your pH may be too low for a soil grow... 6.1 is about perfect for hydro, but very low for a soil run.
You may also have a bit of burn, as the description of the soil & nutes you're giving seems pretty hot.

Try flushing the soil out really well with some pH adjusted (7.0) plain water, letting them dry out for a couple days, and then adjust the pH of your nutrient solution up to about 6.6 or 6.7, and see what happens. You might even want to reduce the strength of the nutes to half-strength.

I think your babies will respond in a positive manner.

Best of luck!