If they see that a player is having an advantage thats not supposed to be or happen, they nerf / remove / change it. There's various sources on the net where a game got updated and just did'nt play as it did before, let alone the avg payout rate. Woud'nt be the first time that providers nerf a few old games in favor of a new released game.
Updates in relation of mobile / tablet compatibility is nonsense; that is obviously getting tested even before release. And smart game devs already have existing and working frameworks for that. No need to re-invent the wheel.
That's tinfoil hat thinking though. If they change the gameplay, they'd have to re-certify the game with every authority before releasing the update. Perhaps they do. Or perhaps more likely, people are just not on a lucky streak.
Or to put it another way; your luck ran out.
I have favourite games which seem to pay me often. They have less generous periods. I don't think the game changed; I just go elsewhere.
RTP is not for the individual really, it's across the board. If I'm getting 95% RTP, someone else is getting 5%. Luck of the draw.