Consider that this is 1 month old. The bag was around 20cm(because it was folded). It has already reached the bottom.
This is 2 months old. And they are growing slower because they are in the same pot(I don't advice it, I had run out of coconut coir that time)!
I stacked another full polybag below, so it's around 45 cm tall here.
You should repot them, but It would be easier to restart. Once they stop growing, they never fully recover. Will be slow forever.
That is true for most tropicals which have long tap root.
Do not put them in direct sunlight the first year, they sun burn very easily.
Regarding the leaves, mine did that too. The first leaves are papery and very delicate. They probably need more humidity to stay healthy too.
Once they switch to the normal leaves these are much easier to keep nice.