when to remove baby java ferns from leaves

[Juicebox]

i got some java ferns from petco few weeks back.. have attached them to a big rock, last couple weeks they have been sprouting new little babies on the leaves and growing roots, i have had some new leaves pop up and grown about an inch - inch and a half..

ive no idea how long i wait before i take these new little plantlets off the big leaves and attach them to their own rocks,right now ive got maybe 6 new little plantlets growing, 3 of them have nice leaves coming in and the other have some roots showing..

as for the original big leaves they are growing on,what do i do with these,i take it they are dying if they are giving me new plants,do i just leave them as they are or do i cut all the leaf off and wait for new ones to grow off the root? heres pics

[Juicebox]

also you can see in the bottom of the second picture,that new leaf that has grown off the new root,the tip of it has gone dark,why is this and is that leaf now no good,is it a dead leaf? any info would be greatly appreciated