Q:

Why do lightbulbs look too bright in my photos?

Lightbulbs used to appear fine in my photos- you can still see the outline of the bulbs and the brightness of the bulbs is just fine. Now, they appear too bright as if they exploded. What seems to be the problem?
I'm using a Canon 70D. I've changed the settings back to their original levels but the problem wasn't solved.
Before:

Now:

A:

Two possibilities pop to mind:
You happen to be exposing the newer pictures more, possibly because the lighting is less bright.  Assuming the previous and current lightbulbs are about the same brightness, that would make the new ones exposed more and bleed into the darker areas more.
You haven't cleaned your lens in a while.

Added
Now that you've shown before and after pictures, another mechanism is obvious.
In the first picture, the picture was basically about the light structure.  As a result, it was exposed as such.  The bulbs themselves are mostly bright but not blown out.  They don't bleed into the surrounding scene because they are not overexposed.  If this picture contained other parts of the room, they would be very dark.
The second picture was exposed for the overall room, so the lights providing the illumination are significantly overexposed.  The small spillover from the lights into adjacent picture area is enough to be obvious, and even overwhelming.  If you exposed the second picture as the first, the lights would look fine, but the people and the rest of the room would be severely underexposed.
Your basic problem is one of large dynamic range.  Small points that provide the illumination for a scene are always going to be much much brighter than the scene.  This is just as true of the sun outdoors as lightbulbs indoors.
So what to do?
Make sure your lens is really clean.  Your second picture shows more diffusion of the bright lights into surrounding area than seems reasonable for decent equipment used properly.  Smudges on the lens can cause this appearance.
Use wide aperture.  Diffraction becomes much more of a problem when small bright dots are against something much darker.  It can become quite obvious at the same f-stop where you don't see affects with other more evenly-bright scenes.  Diffraction effects increase with smaller apertures.  This is basic physics that no amount of clever lens design can get around.
Use a larger film/sensor format.  The reason is not the larger image area by itself, but that the aperture diameter will be proportionally larger at the same f-stop.  The larger diameter reduces diffraction effects.  For example, a phone camera will be the worst, a "3/4 size" sensor better, and a "full frame" (36x24 mm) sensor even better.  After that are various "medium format", "large format", etc.  But, if you're ready for those and can spend the money on them, you wouldn't be asking basic questions here.
Get a camera with good dynamic range.  This is often expressed as "bit depth".  However, it needs to be real bit depth, not marketing bit depth.  There are various sites out there that measure the sensitivity and dynamic range of various cameras.  Since the fundamental problem is one of high dynamic range, more dynamic range that the camera can capture natively will help, if not be good enough on its own.
If you plan to do this sort of photography a lot, then consider getting extra low dispersion lenses.  These cost more, but can make a difference in scenes like your second picture.  They are designed to minimize internal reflections and other causes of light not going to only where it's supposed to be focused.
Since the basic problem is one of high dynamic range, use some of the techniques intended to address that.  These are often lumped into the term "HDR" (high dynamic range).  For example, one method is to take multiple pictures at multiple exposures, then composite them intelligently with software later.  This requires a tripod and may not be appropriate when people move around in the scene.  There is no one magic solution.  In the case of the second picture, one picture exposed for the lights, which then would be largely black where the people are, then intelligently merged with your picture might work.

A:

A few clues in the two photos lead to a couple of possibilities.   

Your lens may be smeared with fingerprints or other semi-transparent material that will cause brighter highlights to blur. Even moving from a colder setting such as outdoors in the winter to a warm, moist setting might cause condensation on the front of your lens which could do the same thing.
The ratio of total light to the brightness of the bulbs seems to be different in the two scenes. The first image is dimmer, but the better sharpness of the image hints at no camera movement and a faster shutter speed, which means the ambient light might well have been brighter overall. The lower exposure value meant the bulbs were captured at a level that didn't cause them to blow out. The second image looks like a slower shutter speed was used. The people demonstrate motion blur and it looks like there's a bit of camera movement as well. There appears to be more noise in the image as well, which would point to a higher ISO setting. All of these things point to less total light in the second scene than in the first image. The higher exposure value needed in the dimmer overall environment means the lights will be much brighter in the second photo.   
It may just be that the lights in the second image are much brighter than the lights in the first image. It's certainly true that the first image is exposed properly for the lights and in the second image the lights are exposed at a considerably higher value relative to their brightness.

