Hi mate, had a look at your diary and to be honest she looks fine to me. Although your lamp is only 5" away from the plant which at her age is a little close. I use a 110W lamp and I'm 12-15" away depending on temps. I hope this helps and happy growing.
Could be the start of a problem but I definitely would not take any action on a little spot like that. Wait to see if it gets worse or spreads before trying to fix it.
Definitely worrying to much btw but that's not a bad thing!