I've fixed longer air stones like those before. Even good quality cylyinder ones are duds from time to time. Using super long drill bits, I was able to hone the insides out, very carefully, opening up more pores from the inside out.
. Also, have had to drill out and glue my own barbed fitting ends on the other sides of the air stone wands, so that the air was being pumped from both sides instead of one. Not to mention adding valves, because no 2 air stones ever seemed to be the same.
I ditched stones for rubber soaker hose, as its cheap, and I always know what to expect. It floats though, so need a good way to hold it down. Make grids or loops, however you want.