Transplanting from a freind of mine

Attachment 275841recently one of my good friends uprooted me two nice little plants one topped but both the same age of 2 weeks then stuck them in a cup and i walked them home i transplanted them into some 3 parts black gold soil with 1 part mushroom compost mixed in and they were droopy at first but regained their composure but i noticed on the untopped plant one morning the bottom leaves are turning yellow from the point of the leaf and progressing leaving it crispy i have been watering with reverse osmosis water with no minerals added and used a couple drops of H2O2 in a sprayer and been misting the soil not the plant it seems to be spreading so my question is can i stop it in its tracks because i have had previous plants i began from seed die in a similar way