where are you.... big city name ... did the heat kick on recently as temps fell??

was it outdoors for summer.. recently brought in ...

how did you come up with your schedule ???... has said schedule been adjusted as the plant got bigger ... why do you think once a week is good enough ... it MIGHT be apparent it isnt ... you should water a plant when it needs water.. not on some artificial schedule ... insert finger and FIND out.. when it is dry an inch down or so ...

the usual answer for the white stuff.. is mineral buildup ... or salts ... of which fert is a salt.. do you fert it??.. i see you use filtered water.. so we hope that rules out the water itself ...

when if the last time they were repotted... media does wear out... and that usually leads to watering issues ... since potting media is simply a water management system ...

im thinking.. as the water runs out so fast ... that not enough is being retained in the media... so that the large plant isnt getting enough water ... it almost is.. but not quite .. so you are getting some minor damage ..

finally.. its not uncommon in fall as we slip into winter ... with reduced light from outside.. that you dont lose a frond or two .. its annual.. its cyclical ... and its normal ... and once they fail.. and you finally cut them off .. bazinga .. all of a sudden the plant looks 90% better ... lets see if it works out that way ...

ken

btw: did you note.. that is appears its putting out 3 new trunks.. for lack of a better word ... it cant be all that unhappy ...