Right now I am using Delta Sunflora and Delta Grimer and they are the only Pokemon on my team with out nicknames. If I don’t like your suggestion, don’t take it personally since I’m kinda picky. All help is appreciated!
Not sure if these names are too great, but Delta Grimer can be Sandman and a name for Delta Sunflora could be Plum ¯\_(ツ)_/¯
I’ve heard Sandman but mine is female. I like Plum though! I’ll leave this open just so I have more options but thanks!
D.Grimer- Mud Made, Melting Sand, Scary, Issa Sand, Sandy (spongebob)
D.Sunflora- Purp, ImHappy, SURPRISE, Mario
Sorry, but I don’t think I’ll use those. But it’s the thought that counts, so thank you anyway! 
I would named my Delta Muk Sink or just Sink sandy and i would nickname a delta sunflora Weed
You probably gave them names already but lol I’m still gonna give suggestions, For the Muk I’D say Muck You and for the Sunflora It’s BigFatFlower