Quarantine my Altum

Hi all I am quarantining my 4 Altums right now. I am using Furan 2 and on the second day I noticed my ph is a little higher than usual and the ammonia is very slightly high. The Furan 2 directions says to do a 25% water change on the third day, does anyone think i should do one on the second day because of the ammonia and ph? Thank you all for your input. I have them in a 20 gallon quarantine tank by the way with a sponge filter on it.