One concern your description brings to mind is whether they were shocked upon being placed into their tank. How many days had the tank been set up? What had been done to condition the water? What temperature was the water? Did you put a little of the tank water in the fish’s bag and let it sit 20-30 minutes? Did you pour off some water and put a little more tank water in for another 20-30 minutes. Did you then pour all the water off (so a minimum number of disease organisms from the shop got into the aquarium) and put the fish in the tank?

Two male guppies in a tank might be a good team to cycle it, though their tails are vulnerable to ammonia burns. If things like cycling an aquarium, seasoned water, acclimating new fish don’t resonate with you, please take a look in the New Tank/Cycling/Setting Up/Water Changing section of Immediate Help. Any number of your questions will be answered. Of course, then there will be new ones off of what you’ve learned. :)

A 2.5 gallon aquarium might be comfortable for them. If you wish to get one or more female guppies, move them to a 10 or 20-gallon aquarium.

As the aquarium becomes established, your guppies should regain some of their color.

If you can toss some low light plants in there, that may help. Not surprisingly, there are a couple of Immediate Help blurbs on low light plants and guppy plants. ;)

Small tanks are hard to keep warm, if they are by themselves. (Some aquarists with what Angelhologram and Maggie and GuppyGirl have described as MTS (multiple tank syndrome) get around the difficulty of heating individual small aquariums by putting them in a room where they are comfortable because the room is heated to a certain temperature.

Are your tanks at least 74-75 degrees F/ 23 C? Especially for the Betta, but also for the fancy guppies, that is pretty minimal.

Another thing, which causes fish to fade, is having light gravel. Most fish in pet shops are young and not as colorful as they will become, but too many shop tanks have light gravel and maybe are also over illuminated. Darker gravel, hiding places, rocks (which you have) give them a sense of security and they will color up better.

When your artificial plants, rocks and tank bottom have stronger colors than your fish, I don’t know what that does to them. 
Others here will be able to tell you a lot more about taking photos than I will. However your do want a place to can set your camera on (or rest the hand holding the camera). That sounds pretty hypocritical from someone who can turn fruit bowls into action shots. ;)

Film cameras may have a faster shutter speed. My older digital camera misses the fish too often in that they have passed the spot I wish they would pose in.

If your camera’s auto focus is focusing on the aquarium glass, move the camera (gently) really close to the front of the tank. If focusing is still a problem, try the manual focus. According to one guy, try the manual focus first.

If you wish to use a flash, can you use a detachable hot shoe or a flash on a cable where you angle in from above and to the side? If you must use your flash attachment attached to the camera, turn off the room light so your reflection is not in the photo. I have seen people take a dark towel and arrange to have it laid over them, the camera and tank side, so as to avoid reflections. A bit of an angle is still a good idea.

Aquarists taking photos in small aquaria like yours have also been known to take a piece of glass and gently herd the fish close to the tank front. The glass piece is set in the gravel and the photos shot.

Both here (miskairal?) and elsewhere aquarists are also taking video camera shots of their fish. Appropriate software then lets them sort through the frames for a “keeper.” The way fish cruise through their aquaria, that is a terrific approach!