in order to change chords perfectly it is required that u, should not put ur fingers indivisually but as a group,
so make a chord ensure that each string is sounding clearly, after u get this lift the fingers about 3-4 cms from the board and try to make the same chord again(all fingers at once)
u may get wrong once or twice, after u perfect this increase the distance till u can form the chord from about one inch from the fretboard,
practice this several times.
and presto u have learnt the chord perfectly,
do this for the three chords and u will be perfect in about a week