From what I'm reading, this is my read of the situation.
It seems that whenever an offensive fails for the rebel side, there seems to be some kind of CW attack.
They were pushed back in the Hama countryside last week and the Russians bombed at the Turkish border.
The RUssians confirmed they didn't do this particular air strike in Idlib.
The Syrian Army confirmed the strike.
Syrian Air Force says they targeted a weapons factory in Khan sheikhoun.
Hayet Tahrir Sham (Al Qaeda), the strongest group rebel in Idlib, says they saw Su-22.
If what was uncovered in East Aleppo after the December govt re takeover is a trend, I'd say that the rebel groups are storing chemicals mainly chlorine (imported from Turkey) in their weapons storage.
The Syrian Air Force blew it up and the agents spread through the village where you have the injuries and death.
Idlib is an exclusively rebel held province. You've had infighting among the groups especially Al Qaeda which has managed to get almost various opposition fighters to fight on their terms.. The Syrian army retreated 2 years ago before the Russian intervention. What's happened in Syria is as the government re-takes territory, they bus opposition fighters unarmed to Idlib. Almost as if to put every type of rebel in one place before they try to fight them all due to the Syrian army's lack of manpower.
From a tactical standpoint, I don't see why the SAA would use chemical weapons when they have the upper hand in the war. Obama and Putin also managed to get that deal in 2013-14 where UN inspectors took the regime chemical stock out of the country. Obviously,there are questions of if that was the whole thing.
Syria is such a fukked situation.