Whilst they don't like being waterlogged, they also don't like to dry out, so if that's happened, that would explain it. The other thing it might be reacting to is either hot days combined with hot nights (they're fine with hot days, but need cooler nights to cope), too much hot sun, particularly in the middle of the day, or a sudden drop in temperature at night, particularly if it fell below 8 deg C suddenly when it had been warm previously.

I've just seen your other question regarding this which has a bit more info - if its not waterlogged, and you've not let it dry out, might be a humidity problem - they like about 40% humidity or above.

</p><p> many thanks, Bamboo!

One other thing that's just occurred to me - if its in the house, then presumably you've got an outer tray or decorative pot in which the plant is standing - when you water, water well, but be sure to empty out that tray or outer pot after 30 minutes - you don't want the plant standing with its feet in water....

Thanks very much, Bamboo.