I'd say the issue with Cumming at the moment is pretty much symptomatic of the whole squad. I know it's a bit of a cliche, but it seems like all players have second season syndrome, whereby they aren't hitting the same levels as they did last season.
Cumming - 24/25 - player of the season contender, kept us in several games and earned us points. 25/26 - good keeper, made some decent saves, but not hit the same levels as last season.
Same applies to so many players, (just a few examples: Helik still a good defender but the goals have dried up. Greg Leigh, average left back, and again not contributing goals like last season. Ciaron Brown, albeit because of injury hasn't yet reached the performed to the same standard as last season.
To me it seems we are in a situation where individuals were over-performing last season and the team benefitted as a result. This season we are seeing players performing to their true level of ability, and unfortunately we are suffering as a result.