Pooping just once a day, or even once every few days as they get older is normal, so i wouldnt be too worried, but it sounds as if his/her sleeping pattern is being diturbed by the light. It's a shame a vet recommended this bulb as it is known tht they can see both blue lights and red ones, without a proper nights sleep they cam become lethargic and go off food.
I would turn it off. Unless the temps drop below 65f at night you really dont need anything. In the wild the temps can drop to 40f. As the above poster suggested, if the temps do drop down a ceramic heat emmiter would be reccomended as they bump the temps up without producing light.
By the sounds of it, the temps arent dropping low enough for your baby to know its time to sleep!! What are the night time temps??
And just to check, what UVB are you using, brand is very important here, and what basking bulb are you using? Also what are the daytime temps? (basking, ambient and cool side?) and what are you using to measure them with?
Buggsy