Just a bit of burning, Plagron Bat Mix can be a bit too "hot" for young plants. (too much phosphorous and nitrogen)
When you start feeding her, use only half strength of whatever they recommend for your chosen fertilizer.
She should be fine now that she is a bit older and can handle the nutrients better.
For a wealth of information regarding soil cultivation, go to Mandala Seeds and click on their "grow guides", it is an amazing source of great research.
Hope this helps, Organoman.