ohnooooo I feel you. I had this problem seeral years ago, it felt as if my whole wardrobe (mostly skirts) were too small. At this time I had not learned to sew so I brought the skirts to a seamstress because it would have ben a shame to give the skirts away.
And she altered them with a new wider waistband or inserted fabric at both sides of the skirt into the waistband (th skirts were all flared and fit me still on the hips)
You could do this on the corduroy skirt and perhaps also add a bit width in general at the side seams.
But there are several other techniques... of which I tried neither :-DD
I think the brown skirt will be easier to alter as it has no pockets (or does it?) and is wider. Here you could unpick the waistband, cut a bt of the heigt from the skirt untill it fits sour waist and then attach a new wider waistband..
here is blog post with a similar methd
https://madenew517.wordpress.com/2014/02/18/the-ive-gained-weight-tutorial/
thanks a lot for the ideas my dear! in my country it is cheaper to go to the store and buy a new skirt than to go to a seamstress. 😕 besides, a good seamstress is hard to find. It's great that you had the opportunity to save your wardrobe! yes, you are right, there are no pockets in the brown one. and in the yellow skirt is. I'm afraid that if I take off the belt, then I won't be able to sew it back on - my sewing machine won't be able to handle it because the fabric is too thick. I remembered: my friend saved my favorite dress like that. she cut off the top of the skirt to the point where the skirt already lay well on my figure. as a result, the dress became a little shorter. but since it was very long, removing a little length did not spoil it. 😃