Word Connections

There are 4 set of 4 words on the grid of different colors

The colors are a clue to the popular Connections puzzle

Though in that case, instead of needing to identify the connections, we are given the connected words and need to determine that associated rule that links them. (ordered below by Straightforward -> Tricky based on color)

GROUP 1	GROUP 2	GROUP 3	GROUP 4
ARK	FINLET	CHIVY	BASK
CRATE	PRY	MICE	CANYON
LUCK	SAFE	MILL	OLD
TARN	SPLAY	SANE	POINT

Each word can have a letter changed to make it fit a category with the rest of the words in the group once a letter is changed in all. For example CRATE can change T -> N to make CRANE which is a type of bird to fit the Group 1 category.

BIRDS	END IN "AY" SOUND	SPICES/HERBS	+"BALL" WORDS
AUK	CAFE	CHIVE	BASE
CRANE	FILLET	DILL	CANNON
DUCK	PAY	MACE	ODD
TERN	SPRAY	SAGE	PAINT

with the lists but in alphabetical order after the changes and reading the new letters in each group the final answer can be extracted of UNDECLARED AGENDA