"Euphoria" may be all about passion and chaos ... but according to a famed astrologer, real-life love still has rules, and not every romance is built to survive -- especially for the show’s star cast.

"StarCast Weekly" host Richard James puts Sydney Sweeney on the cosmic chopping block first, telling TMZ that astrologically she’s intense, and needs serious emotional safety to open up ... which makes her current relationship with Scooter Braun a huge question mark.

In fact, Richard wonders whether this romance is about love ... or a strategic business move -- adding that Sydney's heading into a year of massive personal change, wake-up calls, clarity, and often separation, written all over her chart. Ouch.

Catch the full clip -- ’cause he spills more on Sydney’s year ahead ... and on Jacob Elordi, saying things aren’t looking great for him either, thanks to his on-and-off relationship with Olivia Jade.

Richard says the stars are screaming one thing loud and clear: this one should stay off -- and he breaks down why Jacob needs to hit pause and focus on himself.

But for Syd and Jacob's costar Zendaya, Richard says the stars couldn’t be happier about her engagement to Tom Holland -- and explains why this Hollywood love story is truly written in the stars ... Watch the video all the way through for the full story!

Richard James has a weekly astrology show called "StarCast Weekly" where he goes through all the signs and tells people what they can expect for the week ahead on the streamer Gaia.