Usually means its run out of root room - the new leaves arrive, but can't grow tall enough because there's insufficient soil and nutrients.

Thanks bamboo. Would the only solution be to re pot ? The containers are pretty huge and it's unlikely my sister could fit larger ones on the deck. Could it be dealt with by feeding do you think? At least in the short term?

Not at this time of year, obviously, but the other thing to make sure of is that the short leaves aren't all present on a sideshoot, a sort of baby offshoot if you like - if they are, you can remove that shoot and some root with it and repot it separately. Might also be that those small, short stalks will grow on eventually - I have a Kentia palm on my landing which does a similar thing, some very short stemmed leaves near the base - eventually, they mostly all get longer.