Your L134 specimen appears to me to be in poor condition.; verging on the edge of death.
It should have been given time in a separate quarantine tank and treated for internal flagellated protozoan parasites and worms plus gill flukes.
It should be diverted to a small treatment tank that has a bare bottom with caves and some piece(s) of wood.
I would medicate with metroniadazole, praziquantel and flubendazole in the water.
I would also feed it daily with live worms, frozen blood worms and a sinking catfish or carnivore tablet presoaked in UltraCure PX which contains all the above listed medications. Provide good aeration and an aged filter with no carbon. This specimens, should it live, will need a couple months to regain normal health. The water only needs to be kept medicated 7 to 10 days but I would continue with the treated food about a month.
Here is a what the GelTek UltraCure PX is:
http://www.thatpetplace.com/pet/group/23761/product.web
This is really the best way to get the best meds delivered internally. The same drugs are used in the water but are sold in a more soluble form.
The directions on the UCPX bottle are misleading where it talks about feeding it as drops to the fish. That is nonsense but the product is very good if used per my recommendations.
You should not expect too much. This specimen is in an advanced stage of deterioration but I know how expensive L134 are. I breed them and they are one of my favorite plecos.
Avid Trout fly fisherman. ·´¯`·...¸><)))º>