My guess is from taking a quick peek & the fact that this a chain of shops is that this is a rebranded Chinese liquid. The fact that there's very little info, other then generic descriptions & images, & doesn't say anything about where it's made kind of leads me to think this. Also think if it was their own in-house line they'd be bragging to the rooftops about it. Virtually any Chinese manufacturer will offer a white label service if you buy enough of their product so you can put your own branding on it, although saying that some of the bigger vendors will also do this, so could be anyone . . . sorry.
Your best bet would be to contact the vendor direct & ask who their E-liquid manufacturer is, then check them out.