"Come on strong" seems like a mild overstatement, other than perhaps the NDP in Ottawa-Vanier, where they gained almost 10%; but then, they lost almost that much in Markham-Thornhill, so...?  The Conservatives' vote totals, especially, are in the same range as in 2015.

But then, the oft-overlooked truth is that by-elections are not reliable indicators of anything, even if, of course, parties always prefer to win them than to lose them.