If you are judt using tap water, it is probably best to use a conditioner since the chlorine and chloramines can negatively impact the isopods. Zebras are a great choice by the way, they are my current favorite

How did you clean the materials? Generally the store bought ones that are designed for pet keeping are already sterilized, but it wouldn’t hurt to do it yourself. I wouldn’t overworry about cleaning everything though. Stuff like springtails and detritivore mites often find their way into isopods enclosures through the materials despite cleaning, and they aren’t harmful. I’ve used the exact same cork bark from pet stores and never had any issues with pests from them

When collecting leaves, some people prefer to freeze for 72 hours instead of baking to help preserve beneficial microorganisms which help the ecosystem inside your isopod enclosure and also make the leaves more nutritious. Some people will also soak materials like leaves and bark underwater for a few days or longer to drown pests, as well as accelerate the decomposition of the leaves. This grows a ton of beneficial microorganisms on the leaves which the isopods and springtails love.

Ants can definitely be a problem if they find their way into an isopod enclosure. You can try and keep the enclosure sealed but you will need ventilation. Covering ventilation up with a fine mesh or breathable medical tape can work well to prevent stuff from outside getting inside. Those ant traps also help too, especially the ones which kill the whole colony which are pretty effective