Start off at 24" for seedlings lower to 20" after they are about a week old. They say full spectrum so they will be ok from seed to harvest, however, you may want to invest in some quantum boards after your first grow as these purples are not great
We all think better pics and more details are needed.
I'm going to assume you used a soil heavy with nutes or you possibly thought giving a seedling nutes was a good idea.
I think we can all agree better pics would be helpful.
Also info on the soil used. the fertiliser in the soil may have been to much for that poor seedling.
I wouldn't worry a whole lot about your plants at this point. Don't go dumping random nutes on them that's for sure lol.
See what time bring and keep your normal routine for now