The Summer Bay couple could be set to lose their young son as a spoiler on the soap's official website confirms that "Bianca can't wake up an unconscious Rocco" in a big episode airing on Australian screens later this week.
While Ewing and Gormley have not disclosed Rocco's fate, they told TV Week that the upcoming scenes were their toughest ever to film.
Ewing commented: "Through drama school you get put through some weird scenarios, but this was horrible. It's huge. I would never want to film it again.
"I'm glad I did it, but it was really heart-wrenching. I remember being depressed for a month and cuddling up on my doona [duvet] on the couch."
Gormley continued: "Just the possibility of losing Rocco is very scary. You're meant to lose grandparents, not children. Anything to do with children and sick children - there's just a primal fear there."
Rocco was born prematurely earlier this year and subsequently faced a number of health complications.
While the outcome of the latest storyline has not been officially revealed, show bosses have said that it will have huge repercussions and test Heath and Bianca's future as a couple.
Praising the serial for taking on the plot, Ewing added: "Home and Away is walking that line between a one-hour drama and a soap, and with that comes some higher-impact storylines. It's going to be quite confronting, but for all the fun and bikinis and Summer Bay stuff, I'm glad the show deals with these issues - it makes it a better show.
"It will be harder to deal with, but I prefer the stuff that actually affects you - and this will affect the audience. It was horrendous, but I know a lot of mothers will be touched. It's not going to be easy for people to watch."
Home and Away airs weekdays at 7pm on Network Seven in Australia, and weekdays at 1.15pm and 6pm on Channel 5 in the UK.