General cupped-over appearance of the older fan leaves indicates rootbound. Not just tips, but also edges. If it looks like an upside-down canoe, repot. If it looks like a rightside-up canoe, raise your lights.
:jointsmile:

Edit: Nah, it's neither too late nor too dangerous. Let the root ball dry out rather well first so it doesn't break apart during the repot under its own weight.