OP: training is not a linear thing on a nice smooth curve on graph paper. There are too many variables. It's always going to be lumpy and somewhat chaotic (stochastic?) data and results.

Just be pleased that you're improving and keep it up.

Oh, my guess is it's because you took that 2 weeks off. Coming back from a break is when you typically see big jumps like that. Fresh legs, enthusiasm, etc.