track back the fronds.. and i bet you find out.. its the oldest ones..

which would mean its telling you to get rid of those.. i bet removing the worst 3.. would amaze you on how good it will look.. maybe 4 ...

and by spring.. new vital vigorous shoots will fill the plant back in ...

that said.. it looks like there is a lot of plant.. in a small pot .. unless its a camera trick ...

what is your 'nutritive supply'??

ken

the plant is in about a 10 or 12 inch diameter pot. I think that should be big enough... no? also haven't been giving it much food, just the odd shot here and there with all purpose 20-20-20 fert. haven't giving any in a while, maybe a month or more, you think it could be nutrient deprived?

no .. i think it is underpotted ... and i am wondering how long its been in that pot ...

potting MEDIA.. has a limited life.. it breaks down ... and plants.. need to be repotted every other year or so.. at least ... and the bigger the plant.. the faster the media fails ...

and in doing such.. you replace old used up media ... as it loses its ability to hold appropriate water ...

again ... to mix a metaphor ... those are grandpa aged leaves.. 'feeding' them is not going to solve the age issue .. you said you knew it has to be 'cutback' .. and yet.. you want to assign other reasons for aged leaves ...

when those are removed.. and new come from the center of the plant.. we will watch those .. and see how they are doing.. and that observation will determine.. if more nutrients are needed ...

just cut off the leaves.. and give it a month.. and PLEASE.. report back ...

ken

will do, thanks ken

Only one disease, a rust, is listed.
I would think that it would be difficult to prevent.
Prune away the unsightly parts as minimally as possible.
One leaf looks particularly bad.