Although it has been quite a while since I've held Amquel/Amquel +, is it possible to go thru fine prints on the bottle where it maight say " this product may distort the reading of Ammonia Test when using nessler reagents (1 bottle reagent and color chart goes from clear to yellow)). Thus recommend to use salycylate Reagent test kit (2 separate bottles where color chart goes from yellow to green).
Which one are you using?
BTW, I dont see a need for all those bottles. Waste of your hard earned MONEY, IMO. Just use stresscoat as dechlorinator.
I dont believe in Stresszyme at all. You dont need extra beneficial bacteria in well established tank. Stop using it. And same goes for Amquel/Amquel+.
As far as ammonia in pH 6.2, I would not even worry if level was lot higher. But if you raise the pH above 7.6 in presence of ammonia, asking for trouble.
Even at 6.2, never lost the BB but would like to see stable pH close to neutral for most tropical.
For now make sure it does not go any lower.
What types of gravel do you have and for how long?
What is pH/GH/ KH/NH3/NO2/NO3 of your tap water?