An alternative interpretation
The question asks, does casting dispel magic on one creature affected by bless also end the same bless on the other two creatures within range.
The accepted answer to this question, citing Sage Advice, says that the dispel magic only dispels the bless on the targeted creature, not the other creatures affected by the bless.
The accepted answer is significantly upvoted, and accepted, and it's well-reasoned, well-cited, and well-written.
However, there's another way to look at the issue.
The dispel magic spell says:
Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends.
The relevant Sage Advice Compendium entry says:
If dispel magic targets the magical effect from bless cast by a cleric, does it remove the effect on all the targets?
Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets.
There is a lack of clarity in Sage Advice on dispel magic and targets. It says "Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets." The word "target" reads as if it means only creatures as targets, invalidating the "magical effect" as a legitimate target, which is what the asker asked. So the way it reads, the implication is that only magical effects on creatures (or objects) are valid targets of the spell, which means you can't target a magical effect separate from the creature affected, but the spell says you can.
However, as shown by the many questions on dispel magic, the debate can be endless. Some readers will agree with my assessment, others disagree. Another way to resolve the issue is to home rule an adjudication process allowing the dispeller to explicitly end a magical effect within the range of dispel magic.
A modest home rule
We resolve this particular issue with dispel magic at our table with the following home rule:
When casting dispel magic and targeting a magical effect, as opposed to a creature or an object, describe the magical effect you want to dispel. If in the DM's judgement you have successfully described the effects of an ongoing spell, it is dispelled according to the rules in the spell.
Example 1: Last turn, an opposing cleric seems to be bless several of their allies. I cast dispel magic on the nearest one. The bless ends on that opponent.
Example 2: Last turn, an opposing cleric seems to be bless several of their allies. I cast dispel magic, saying, "I dispel the spell that guy just cast on those guys". The bless ends on all three opponents.
Is this truly a home rule, or is it simply an interpretation of the rules? Well, calling it a home rule eliminates the arguments about whether it's RAW or not.
We've used this at our table successfully. There's potential to argue about whether the dispeller even knows a magical effect exists, and with identifying it, but that is inherent to dispel magic, and not this home rule, and so far the DM has made a ruling and we've moved on.
Admittedly, for us this situation only comes up rarely, so we have not extensively playtested, but it has worked so far. YMMV.
User volferine brought up a point in the comments. The text of the spell says "Any spell of 3rd level or lower ends." At our table we interpret that to mean "any ONE spell" ends, and we have not really encountered enough edge cases to have to deal with it. But this is a great example of how the existing wording of the spell leaves a great deal of room for interpretation, and just about requires any DM encountering the spell frequently in a campaign to have to deal with many unusual cases.
To the OP
As so many other questions do, this essentially comes down to "ask your GM". But when you ask your GM you can provide a suggested interpretation or home rule, and the great thing about home rules is that if you don't like the one I've presented here, you can suggest a different adjudication.
Some other RPG.SE Questions on dispel magic and "magical effects"