Shaun Weiss has some fans thinking he relapsed on drugs ... but he says folks are reading way too far into a video he posted online.

The "Mighty Ducks" star shared a video Wednesday on Instagram, talking about how blessed he is to be paid to travel around and interact with fans ... but his physical appearance seemed to throw people off.

Shaun, who recently celebrated 4 years of sobriety, is looking kinda thin and he has a red substance smudged between his eyes ... leading some to wonder if he busted his head open, even though his caption says it's "consecrated ash from Sadhguru."

Shaun tells TMZ ... he's still 100% clean and has not relapsed.

He says he's doing great and has never been better, adding ... "If I ever need help I promise I will reach out to people. No going backward."

As for what's on his forehead, Shaun tells us it's from his "spiritual practice." He says it's supposed to "activate my third eye."

Shaun says he's getting into the inner engineering teachings of Sadhguru, a famous Yogi ... telling us, "It has been a game changer in terms of my overall balance and levels of joy."

The video that first sparked relapse concern among fans was on Shaun's page for about 5 hours until we talked to him ... and he's since uploaded a new video where he wipes off the red substance from his face and says he's fine and there's nothing to worry about.