IME; Copper will oftentimes suppress symptoms of brook, but won't fully eradicate it. Which is why you may not be seeing signs.
A Ruby Reef Rally bath, followed by transfer to a sterile QT is sometimes enough. If you put the fish right back into the same QT, they will just get reinfected.
So the plan - Ruby dip and then right into new QT tank with general cure + kanaplex and furan.
I’m still slightly worried it may be velvet and not brook. Should I continue the copper treatment as well in the new tank? Or since I am transferring them to a new tank I will be okay. By the time the new tank is ready and the dip takes place they will only have been in copper(.5) for 6-7 days.