Dying sedirea japonica, please help!!! :(

[merytt]

Im in trouble whit my sedirea, 2 of its leaves have follen of.....i really dont know what to do... When the first one had follen, i remounted it and put more spag because i tough it had not enough humidity. Its growing on a branch, shag beneath roots, not to close to the growing point of leafs. I tought it may help stimulate roots to attract them grow more. Its not that it has bad root growth, just i tought the water was drying too fast to keep some humidity.
I spary it every morning, then watch that te water doesent get between leafs and edc. I fertilitize it really feek and one a week, water whit rain water. its growing under light in an open aquarium. Humidity from 65% to 97% after i have watered. Temp 18,5 -23,9 this week.

So where did i go wrong..... im sooooooooo sad i cant describe it...