Cant help much. Not too sure if it's a Trachycarpus fortunei but some sort of palm. Same with yellowing leaves, underwstering, overwatering, need feeding or maybe they are just old leaves dying off same as fatsia leaves do.
It does look like Chamaerops. If it is so, it is a (weirdly) xerophyte palm (from Portugal, my father's land!), so it does not bear too much water. Have you checked drainage in the containers? As they are so close to the ground, it might be that water pools under them, damaging the roots. Just a thought, though...
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Same with yellowing leaves, underwstering, overwatering, need feeding or maybe they are just old leaves dying off same as fatsia leaves do.