Why are they not growing rigorously?

yep... mouse and dutchdoobie are right. More light exposure... also they need an average of 60% humidity...

High YummyLegg, They stretch a lot so they need a bit more light! If it is possible try to place them somewhere with 18 hours light a day! They look healthy so they will soon when the leaves are larger grow a lot faster! Happy Growing! 😋

The one in the paper cup ts#2 did not get enough light and that's why is stretching so much. You might want to brace that stank with a stick, if it gets windy it could blow over. More time and light/energy is needed for these little ones to beef up. Once they start getting the things they need they will take off but as of now, they will be suck a bit behind some of their other peers because of this. Still will grow into a lovely plant though if you care for them [properly. I would look into transplanting ts#2 once it develops a moderate rot ball. That cup is a bit to small for it. Best Of Luck! ***disclaimer, multiple people are answering all questions as there is a contest called GOTM, when a user is selected as the answer they get a point. Please see the contest page for information regarding the details: growdiaries.com/giveaways/GotM-August-2022 Please note, when you reply to anything on the questions part of Growdiaries website, no one will be notified of this. Not even if you use a "@" tag in their name. Best to reach out to them in DM using your inbox, it can be found in the bottom right hand corner of the site. It's the small paper airplane button, it will be highlighted green if you have new messages***