No. Wenu doesn't tell us if the noun is plural or singular. Possessives referring to nouns in class 1/2 (M/WA) start with "w-" whether it's singular or plural.
mwalimu wenu "Your teacher"
walimu wenu "Your teachers"
-enu is "your" when addressing more than one person. (Silly English makes it ambiguous). If you're talking to just one person, it's
mwalimu wako "Your teacher"
walimu wako "Your teachers"