K.H.
Yes it could be a stage , they like to push boundairies to see what they can and cannot get away with. Having said that though , he may never go back to eating the foods that he once did , my son was a very good eater and then at 15 months he refused all the things that he liked (and still does , he is now 6). Your mom is right , don't cause a fuss , don't try to force feed. Just keep putting down the foods that you are (the same that you are eating) and if he doesn't eat then take it away with no fuss and don't offer any alternatives. Hard yes but the best thing to do in the long run. A child will not starve themselves and once he realises that you will not back down he will give in eventually.
Good luck