Is the white stuff in the pictures mildew? If it ...

Ya man as everyone has said it's probably dust and or build up from working in the tent , do you foiler spray ? Mist and dust collecting on the walls of your tent is easy to get rid just wipe it all down with water and bleach in a spray bottle 1/8 bleach to water and I use the disinfecting wipes on the outside of the tent as well . Best of luck with the grow ..best case is to always keep calm and just take a common sense approach

There honestly should be no mildew as long as you have a good air flow? What’s your temps look like? I remember when I first started growing I would over think everything or think something is nothing for weeks I thought I had bugs flying around my tent come to find out my fan was up to high casing the dust partials to go into the air making it look like shit flying around. They ar plants 🌱 weeds even if they get sick they get sick pluck them. But use disc infection wipes to wipe everything remove your plants for a couple hours set them in sunlight by a window happy growing 🌱🤙🏼