There's a lot of content here... so I'm going to go very first impressions:
Flecks of Jupiter: Nicely drawn and presented comic. The solid art does make a good first impression, and then it sets up an intriguing idea about characters from another planet whose appearance changes. Unfortunately, it then gets a bit too bogged down telling me too much stuff about details of life on Jupiter that aren't immediately relevant to the story, and slow the whole thing down.
I also kinda feel like if you wanted to come up with a planet with all these fantastical characteristics described in detail, maybe it would have been better to invent a fictional one, rather than use Jupiter, a planet close enough that even with a pretty casual knowledge of astronomy, I was like "...this contradicts scientific facts I know about Jupiter." For me, it was pretty distracting, but a lot of people would probably be okay with it.
I had a skim ahead, and it seems fine, but doesn't seem to have a strong, driving plot. It often establishes characters or ideas... but then doesn't really do anything with them. Maybe it's just too slow-burn for my taste! Other people seem to like it!
That Beautiful Melody: Immediately, gotta say, great cover! It's really nicely presented, good composition, lovely sense of drama and movement... and really pro typography! But you should definitely also add a banner on Tapas just to add that extra bit of presentational pizazz!
The art is.... Well, it started out very impressive, and I was there like "holy crap! That's well-drawn!" ...but then I started to feel like "well referenced" might be a more accurate thing to say, because the more I looked at it, the more familiar a lot of the poses felt... and it's hard to stop noticing how much the love interest character looks like Sasuke. He really looks distractingly like Sasuke. But a more important downside to how heavily referenced the art is, is that the quality varies wildly, from incredible to a bit rushed and scrappy, and the rushed, scrappy panels get more and more common as it goes. Plus there's a tendency for some panels where something specific had to happen, like somebody waving through a window at somebody outside, look weirdly disconnected, and the characters aren't looking at each other, presumably because whoever drew it couldn't find a reference for waving through a window facing the correct way. It's a bit awkward and distracting, and I'd urge the artist to practice building characters from scratch with their own designs and construction for better consistency and clearer storytelling.
The background choice of putting a watercolour filter onto backgrounds is interesting, bold, and almost works. I think if they had a little more manual touch-up in places to just reduce how "photoshop filtery" they look, it could be really cool and distinctive while staying pretty quick and easy to create. The colour palette certainly works well.
Story-wise, this one is again, a very slow-burn sort of romance, and doesn't have a particularly strong unique premise. It's not something that'd appeal to me, but I've never really been into slow-burn, and prefer slice of life with a bit more drama or comedy, or a stronger central theme.
Waiting Under the Stars: Well-drawn cover let down by weird layout choices. There are big black bars top and bottom, but then there's text over the image...? Why not put the text in the big areas where the image isn't? There's a lot of bitty text all over this cover, and it's a little baffling. The title is too small, and there are too many things written on it that aren't the title. Again, also, no banner, which is a missed opportunity. I think a better cover with nice typography like Beautiful Melody's and adding a banner would really help this one, because the art is good, and the cover could really show that off.
The art is soft, appealing and pretty consistent, and fits the tone of the story well. Occasionally the characters are a little awkwardly integrated into the 3D backgrounds, but it's not too bad. It's the most consistent of the three, and the one that uses art to tell the story the best, which really helps me get into it without feeling distracted. This artist makes good choices about where to place the viewpoint and draws character interactions where you can tell what emotion is intended. The style is simple, but the visual storytelling is very solid, props to this artist.
To me, this one has the strongest story, because it introduces the two characters with a cute interaction... and then sets up an intriguing mystery; "why do these people who were once so close now not talk to each other?" and then cranks up the mystery with "why is he writing to her, but won't speak to her?". I actually was intrigued to find out more. There's a bit more emotional intensity to this one, and I think taking inspiration from real life added a sort of... realness and uniqueness to it. The scenes don't feel like ones I've seen in other comics, they really feel like I'm reading a unique story, with well-realised characters rather than comic archetypes, and real events and feelings rather than tropes. Definitely overall my favourite of the three.
You're clearly a very productive and dedicated person! I can't believe how many comics you have going! I like that you're trying a lot of different things, and working with various artists on different projects. Judging from how long you're able to keep working with the same artist on these, you must be a good person to work with, so that deserves some praise too; a lot of creators struggle with that! Being able to work in a pair or team is a really valuable skill in comics.
Honestly, just keep at it. Try to remember to add banners on your Tapas works, and maybe consider getting your artists with strong design skills to help out on covers by ones with good drawing, but less design knowledge or experience.
I think Waiting Under the Stars really shows that working in a bit of your own life experience adds some spice to your work that really punches the storytelling up a notch, so I'd definitely urge you to keep trying to do that, even when you're writing more fictional stories; use real feelings, or take inspiration from real people and experiences.