His bloom setting is not a mistake in this particular FX, due to simple shape, not so much detail and it is a bomb, but in general you should avoid over-blooming like what he did. In the short run, it will kill any fine detail you may have in your FX, make your color choice uglier and less interesting. In the long run, that will make you addict to it and ruin your artist-sense (if you know what I means).
Bloom can be used to hide a lot of problems, but not every game will allow you to use it, or use your setting. You must follow game’s postprocess setting, so learn to not rely heavily on it to make your effect looks good.
You can see the shape of the sparkles at the end of the explosion is almost unreadable (only readable when they are eroded halfway). For example in this screenshots, the details where I mark is bleeding. That bleeding is fine here because it has simple shape and no detail, but an effect with more details will suffer from that.
Bloom is great, as great as other effects but learn to use it right. If you check Florian’s portfolio you will see he doesn’t do this on every of his effects, he knows what he does. Just warning because this’s a common newbie mistake when try to learn from other good effects. These effects often have so many layers on top of each others so newbie will try to replicate what they can SEE, not what actually matter.
Oh and yes, you did that mistake in your scene. I just don’t talk about it since you have many more important things to work on.
If you want to learn to make good effect without abusing postprocess, check out Sirhaian’s tutorial and his scene breakdown. These are a little outdated but still teach you a lot on how to do VFX right.