There's some evidence to suggest that the Soviets used weaponised Tulameria against the Germans at Stalingrad in OTL.
It depends when they're used of course, and to what scale, a small use of gas to gain a minor local advantage might slip under a radar, or Stalin might be convicted to go in for a Pound if he's going in for a Penny, and as much widespread use as possible. If he did this in 1943/44 coupled with Soviet artillery and air supremacy could truly devastate the German supply chain, still heavily reliant on horses. Of course by then there was less sense incentive for the Soviets to break the chemical taboo and risk the situation degrading into stalemate, as Guderian had spoke of when he considered gas in Achtung Panzer. A more likely case would be Stalin deploying it as what he might think is his last roll of the dice in the dark days of July-August 1941, but then it's impact would likely be localised at best, considering the Red Air Force being so much wreckage and the front being on the verge of chaos, with the Germans being in a far better position to retaliate. Either scenario could end well for the Soviets, but both were also too likely to backfire to be worth it.
Either way, the end comes, as ends often do, in the shape of German Cattle, and British Linseed Cake.