I have just a basis 4-5 tier dehydrator. When i try to dehydrate banana's or strawberry's even if i cut them large they shrivel to nothing. the banana's turn mostly dark brown/blackened. It seems to do apples, oranges, pineapples okay. any suggestions on how to do better at banana's? my daughter loves them and id like to make some chips for her. FYI- the dehydrator i have doesnt have settings or speed, its just one mode. ive tried leaving it on for different times etc but it didnt make a difference really.