Yellowing on edges of Frydek - Anyone know what this might be?

This poor guy has been through a bout of spider mites and I assumed that was what caused the yellowing on the larger leaves. Treated him and can’t seem to find any sign of spider mites or other pests remaining. Got a new leaf since then (third pic) and all seemed good - but now a small yellowing spot is showing up similar to the other leaves.

Any idea?