Depressed betta?

My halfmoon, Venus, has been in this 5gallon tank for a little over a month now. He used to dart and swim all around, now he seems to just swim slow and float. He doesn’t seem sick, just not as lively as before. Maybe I’m overthinking? It’s just him with two snails. He’s very feisty so I’m hesitant to put any other fish in with him. My plan is to put him in a 10 gallon because I think he needs more room, but that won’t be for probably another month due to time. Water parameters are good: ammonia and nitrite 0, nitrate under 5
In this picture he’s at the bottom. He doesn’t stay there all the time tho, he just kinda lays on the plants or in his house lol

Most of mine rest more than they swim. I have 2 that are always busy with bubble nests but the others, meh.