I would bet for the previous overwatering issue it cause such issue, you can search for over wating issue and how the leaf looks like, these nice gals hate too mutch water it's very important as someone said above you water but stop unless the soil is dry (touch the soil to check if it's dry) if it is it's time to water but not a lot again :)
anyway that's how I see this issue but I could be wrong.
Good luck the rest looks perfect nice jobs for a first grow, my first grow was so shitty I didn't even show it to anyone and got 15gr out of it lol, but how it is going you'll get get some nice and huge buds ;)
Ktims420 
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Hey there!
Good luck with your Blue Dream'Matic=)
Let us know if you need anything :green_heart:
ps. as far as watering goes, check the surface of the medium, if it's dry, you can start with about 500ml of water around the seedling and work your way up as you see fit.
@Ktims420, You're doing great! She's looking nice and healthy =)
@Fast_Buds, growing two different strains right now they are my first time grows so I was waiting to get off too a decent start , wouldn’t want to put your name on a plant I don’t grow well lol . Looking awesome tho loving the FastBuds :raised_hands::skin-tone-2: