Looks to me like a bit of overwatering. Let the soil dry-out a bit between waterings. Letting roots sit in wet soil will cause damage.

Also, keep an eye on your milk jug plant. The light coming thru the plastic will kill exposed roots, and will likely cause algae in the soil. (especially with consistently wet soil)
Rusty Trichome Reviewed by Rusty Trichome on . First Grow - CFL G'day and thanks to all that contribute and leave supportive comments on my fantastic grow journey! Ok! So my frist grow, I'm excited about this upcoming journey! So ill give you a bit of the history behind this grow before I get into its current stages and pictures. I have only just decided to do a grow log on my plant as if I run into any difficulties you guys can help me out, cheers! - Germination of 3 seeds that took 3 - 4 days to grow tails. - Planted and took 2 days to sprout. Rating: 5