Where are they? I have just caught D. Treecko
D. Mawile is in hidden grotto on platform where red rock is. For Petlil you have to battle or run from pokes on static encounter north west flowerpots (or something like that). After encounter go to another place and then back to reset static pokemon. I think on 4th or 5th time you get petlil there.
thanks!
You’re welcome!
where is exactly the hidden grotto? I spam C in the red rock which is the the site of the Manaphy statue and anything occurs.
Give me 10 min I’ll post a picture
Okay, thanks!
Oh, shit I see now hahaha I thought it was in the rock, thanks!
Probably my bad. I’m not native English speaker and last time I really used English was in in high school like 4 years ago so… I find it difficult to describe locations. I am more like point and show kind of person. 
Haha not really, I was used to speak well but your describe was good, it was my fault that I don’t look carefully!
There is also Delta Karrablast who appears at the mysterious stump to the west of the grasslands during a full moon IRL