The catch circles in game have been reduced drastically. Exp. gain must of been too OP so they decided to shrink it?
This might just be a side effect of Niantic implementing the new update, let's be patient and see how this works out. Right now there is a ton of glitches in the game, and I'm sure they're working on all of them.
They've not all shrunk, for me a Geodude and Ponyta's circle had expanded massively.. I suspect the game is a bit wonky while they set up the gyms because I don't see any mention of these and legit changes anywhere
The circles on sun kern and weedle are practically microscopic and now magikarp is huge