We’re also unsure if he’s a he, but we refer to him as such

Hello, we’ve had our robo hamster for less than a year, & we’re unsure how old he was at the time of adoption. We’re also unsure if he’s a he, but we refer to him as such. He’s usually very energetic, even during the day when we have tried to pick him up, even though he’s nocturnal. However, today we noticed a couple of concerning things. Today, his eyes are remaining squinted/shut & he allowed us to pick him up without running. Today when we tilted him to check for responsiveness, he moved his legs a little. That’s not like him. We’re concerned mainly with the lethargy and the closed eyes. We haven’t noticed changes in sleep, diet, water intake, stool, or his skin/fur. He’s housed alone. There is nothing observable going on with him, even his closed eyes remain clear of crust or debris.