But they grow very fast (the pleco) and are active (loaches) and the extra foot of space is valuable.
Plus, these fish get large and the width of the current tank would be too small for these fish to turn around properly and comfortably. The loaches especially need a good sized footprint in a tank.
And plecos have some monstrous bioloads, you will find yourself eventually having issues with water quality in a smaller tank and you may end up having to do daily water changes worst case just to keep your nitrates under 40 because of it.
Thats why itd be wise to upgrade to the proper size within the next few months. Not saying run out and get it tomorrow, as they will live in it fine temporarily as a grow out, but it wont work past a couple months sadly. These are some very hefty fish.
If a 150gal+ isnt doable, an option would be to find a home once these fish get too large for this tank. Some people do this too.
Then afterwards, get some similar but smaller fish.
Yoyo loaches and a bristlenose pleco would make a fantastic group for a 50+