I know this ain't about sps but, seriously bro? 2 big blue tang in a 2x1x1ft tank? You do know that even 1 blue tang for a 422 is small enough already. And they look way too big to be in your tank. I know i probably offended you with this post of mine, but i myself find it wrong if i don't do anything. I know you probably cant upgrade or have a big tank but thats not an excuse to be keeping 2 large blue tang inside a 2footer. you have no idea how much space and current(flow) a blue tang or generally any tangs require..
I hope you seriously consider rehoming them..4 footer for a juvenile is ok, but ultimately (and at the size your blue tang are) they will need at least a 6ft tank. No hard feelings but this is just wrong IMO...
Just my 0.2cents.