In my opinion, you are trying too hard and on too many leveles at once. Restarting the tank is useless. Just be consistent and patient with water changes and prepare the water with alder cone exctract (soak the cones in RO water for day or two, than just use the exctract and do not put the cones in the tank, big handful in one liter of RO water should make the job for about 10 liters of water. I add extract from one big catapa leave that I soak in a bucket in the meantime when preparing the aldercone extract, you transfer that leave in to the tank with water and remove it after another 2-3 days), beech leaves (not green of course! may stay in the tank for very long time, almost do not spoil and make great bottom), Terminalia catapa leaves need to be removed after 2 weeks at the worst. If you bought peat, you may drop the water over it. This way, the rest of the ions in your RO water will exchange for H+ and make the water very acidic and stable. Using more types of these natural substances makes the water better and more stable. Avoid any other chemicals that do not come from these natural things. Also when feeding artemia, make sure you wash it on the sieve with RO water so that the brine solution does not get in to the tank. If you are putting some tap water in the tank with your pippets, the pH will of course go up slowly again.
Regarding the mosquito larvae, they help, but they are not necessary. They just contain substances that help trigger spawning, but these are in many other foods, cyclops for example works great too.