My husband has gained weight

So my husband and I are not the slimmest people, but recently he has put on a significant amount of weight. I would say over 15 pounds in one month. I was working on losing weight before I got pregnant and had lost about 15 pounds. He wasn't trying at all. It has gotten to the point that I have had to buy him 2 new sets of shirts in the past 2 months because they have gotten too tight on him. I don't know how to nicely say something to him because he thinks he is fine, but he has started snoring recently and I think it is because of his weight gain. I'm just worried about him. SOS