Bro,
Don't worry about the crossing of your xb. This size u can try meal worms. WTT is not to help your fish cross. It is just a commercial way of making xb looked like fully cross due to the white environment.
2 cents worth:)
for xb wise... traditionally they do not have big finages and mostly are bullet heads...;) But nwadays alot of mixing already so wanna get back traditional is very very hard..:)
Bro, I would suggest u to put a heater of 30degrees in addition to ur WC and salt(should be 1/2 to 3/4pack of 1kg shld be enuff) and also change ur filter wool to a new set. It should be able to heal within a week.=). Cheers. This regime is for raise scales due to parasites or water parameter...