Hi.
I have experience in keeping both Marulius and Marulioides.
The fish you have there are 100% Channa Marulius.
They are not "isabella" or anything like, just Marulius.
Forget any crap you hear from sellers etc, those fish will reach waay over 100cm and very quickly. (I have been there, trust me)
They are also very nasty buggers. They get real nasty at around 30cm. This is when they will kill anything in the tank, including their own.
Unless you have the means to house these monsters, I would suggest taking them back and getting something more suitable for home aquaria.
Good luck!