I'm gonna guess pH and/or temp shock. Most fish don't handle temp drops well, especially if they are already stressed. I think the acclimation could have been better too (no offense). Twenty minutes isn't very long if the parameters weren't pretty close to begin with. I'd have gone at least another 20 minutes and continued adding tankwater every 5 minutes.
Also, I'd do away with the dip stick tests and get the liquid kind. I don't trust dip tests at all and I've seen 3 strips give very different readings from the same sample.
All in all, I think they are in some sort of shock. Whenever I've suspected that I keep the tank dim until they start looking better (dim not dark). Otherwise I really don't know what to do for them. I used a hefty dose of NovAqua+ a few times but that was more due to their injuries than shock. They recovered so, IDK just another idea.