Have you grown in the 2qt rez before? Ultimately you are gonna need a ppm meter to track the levels in your rez. 3% h2o2 is weak, it's what I use. 32oz's in a 5gl rez so you probably could get away with 40ml's in your rez, even 60ml probably wouldn't hurt.. I have a 2qt container that I set up to practice cloning with. use a bowl fill with h202 & soak the roots for a minute or 2 or use a spray bottle filled with h2o2 & spay the heck out of the roots. it worked on my plants roots. It is still only a temp fix though. clean all of your equip, rez, air stones Even the air lines. I soaked all my stuff in water & bleach mixed 10:1. rinsed withwaterafter & then soaked with h2o2. after everything is dry wipe it down with a damp(barely) paper towel you may notice a powdery film similar to soap scum like from the shower/tub. the only way to remove this film is wiping it down. I tried scrubbing etc... the scum still showed up after the stuff dried, but wiping (more like rubbing it) it out with the paper towel worked. I am wondering if trying some of that micoorhyzae(? spelling) stuff is what i need. It's been the same plague with every experiment I have done. I have probably spent more on the so called tips & tricks than if I would have just bought the right stuff to begin with. However not knowing what the stuff is & how to treat it... just goes with being a noob to gardening in general in my case. the problem for me started as a whitish slime that eventually turns brown & finally shows as root rot of some type. You can use the h2o2 for a temp fix. you'll just have to keep reusing it. As for your air pump, I use a aquarium pump for up to a 60gl aquarium w/dual airlines. However as far as the air stones go. I hooked both air lines to a T & then to a single stone & now I get the type of bubbles I should be getting.
good luck with the growing man!