Becca,
I don't grow in any coir but I do use a peatmoss based mix, with some perlite, otherwise it gets to moist and not enough air in the center of the pot. I wonder if you would adjust your mix to increase the air to the middle you would have a better outcome as far as the roots grow. Perhaps with bark, perlite or even charcoal.
I'm not a fan of slotted pots, clear, green or clay slots. I've used them for a couple of years and found the dried out the roots on the (outter edges to much) leaving the center with too much moisture. Then there's the roots getting out and the ramble factor
Some folks do like them and use them with success.
It's not uncommen to have a few roots die off. This can simply happen with changing out the overall mix aswell. It's good that your lowii has active roots.
I'm curious about you lighting and tempts & humidty