Are my houseplants affected by pests?

Hello there!
I've been collecting plants for exactly seven months. I've always been careful when buying them, even quarantining my new plants. I've been worried about them for three months now because I've seen a thrips on one of my plants. Since then, I've been using chemicals and beneficial insects. I still haven't been able to determine where the thrips came from. I think it came from the garden.
I'm currently having a problem: some of the new leaves on certain plants don't look very healthy. I'm no longer sure what it is or what to do.
Maybe someone can diagnose me or give me a tip. I'm really at my wit's end 😅

Strangely, only new leaves are affected, not current ones. Could it be due to the chemical spray that got into the substrate?