I think the problem is that you are not used to it, sure your first two fingers are always stronger, but that's not
all, they're also used to move in different ways and so on, the strength isn't the real problem.
For example, try to type just with your ring finger and your pinkie, it's pretty strange, but after a few hours you
get used to it, the fingers won't be stronger at all after that time, but they're used to the moves, it takes a bit
more time on the guitar, but try to play strange chords, spread your fingers, play hammer ons and pull offs with
your two weaker fingers. Don't force them too hard, you don't have to press the strings very hard.