Diminutives from Marta: Maruszka, Marusza, Marucha, Maruchna, Marocha, Marsza, Marszka + many more
I have never come across any of the above being used as diminutives of Marta. To be honest, Marucha and Marocha
sound almost obscene and I would never call them diminutives - where on earth have you heard them used?
Pet names derived from Marta - Martusia, Martunia, Marteczka, Martuchna.
As for Maria - Marysia, Marusia, Maryśka, Maruśka, Marysieńka, Marynka, Marylka, Mania, Maniusia, Marysiunia... the variations are almost endless ;-)