It could affect the Pleco. I would decrease the amount of salt to 1 Tbsp per 10 gallons instead of 5 gallons. Plecos are a little more sensitive to salt, but he should be ok at the 10 gallon dosage.
Wow, i'm suprised he hasnt gulped down the Tiger Barbs yet. Lucky little guys.
Just a little side note. Wardley products are crappy. They contain corn meal which is indigestible to fish and many other animals including us.
I would switch to a better brand. If you have access to it, i would get either Omega One, or O.S.I or HBH. Those are better IMHO.
But even Hikari is better than Wardley since it doesnt have corn meal.
Just my $0.02 on the food