Shiny hunt method with herba mystica not working

[tonytera14]

First off all, I wanna apologize if this is not the correct topic for this question, but I have this doubt and I'm a non-English speaker and need some help.

When I started playing Pokémon Scarlet & Violet in Switch, I used to make shiny hunt using the sandwich method, with herba mystica. It used to work well, with lots of spaw and one shiny for hunt. 

But, since the realease of the SV's DLC, the method seens to not work at all! The spaws are the worst, almost none pokémon showing (unless it's a mass outbreak - that naturally already have a huge spaw) and zero shiny (even in mass outbreak). 

I don't understand what it's happening, the method used to work so well and now looks like it never existed (the last time I had a sparkling level 3 in Blueberry academy e no shiny appeared). Anyone have the same problem? Or know how to solve it? Thanks a lot!