I'm having a similar weird experience with Dr. Tim to start a QT tank. I've used it with success in the past several times adding with fish and getting minimal if any ammonia spike but this is different.
Using it to start up a 30g volume quarantine tank (in a 40g breeder). Added Dr. Tim ammonia to 1ppm and then added 2oz Saltwater one and only from a 4oz bottle (looks like lot ##317 best by Jan 2018, amazon purchase). It was kept at about 60F in my basement. Only filtration is a foam filter, a marinepure block and some rubble that came from an established aquarium. Initially ran a small powerhead but then I decided to stop it and see what happens. Temp at 78F. No skimmer. No livestock. No lights.
After 1 week, Ammonia never budged so I added the full 4 oz. 1 week in. I didn't check nitrite/nitrate since I assumed that the Ammonia would come down. It's now on week 2 and there is still 0.5-1ppm (ATI test kit) of ammonia. There are 0 nitrites (Salifert) detectable and Nitrates (Salifert) are at 5ppm. That feels low to me unless the cycle is just starting now.
Any thoughts? Is this a bad lot for some reason? Just keep waiting? Add more rock from my DT? I sent an inquiry on the Dr Tim site.