signs my blue tongues are fighting?

[obsessed with Blueys]

i house three blotched blue tongue lizards in one indoor enclosure.
two of them were born in captivity and have shared their whole life (even before i got them) and the third i've had with them for a year, ive had the first two for just under 3 years and the third just over a year and never had any issues.
but recently i have been reading up on shared housing and EVERYTHING says not to do it..
but i don't really have room to seperate them, is it irresponsible of me to continue keeping them together?
should i work out how to split them up? the last thing i want is for them to be unsafe...
again, i haven't had any issues yet.
however i was just holding one of my boys, i picked up a pencil and waved it around a bit (doing some homework) and he flinched and closed his eyes.
ik this isnt abnormal for them to be scared of something that could hit them but he seemed really scared and now im wondering if hes being bullied by the others? another thing to note is that he never sleeps with them during the day, only at night.
i am building a new hide so he has his own space.
hope this makes sense!
thanks