The smaller striped is a Striped Raphael Catfish I think.
The Pleco has a mottled coloration naturally. The white sand substrate is much lighter than its color and it might be a bit lighter color trying to blend in.
Also many kinds of Plecos need (some must have it for digestion)/enjoy driftwood to chomp on.
In the bottom pic it looks like either streaks on the glass or are they on the fish?
I have has a Raphael shed some skin before, so it could be that.
Were these fish from an individual? Were they from a tank with a lack of care?
Are you familiar with the nitrification cycle? Is your tank just newly set up?
The link in my signature has an article for getting started and explains the nitrification cycle as well! Very useful information too.