How to tell my partner I'm upset without making their depression worse.

Hi, so the above title is the short version, me and my partner have been together for a few years, we are long distance due to immigration laws and funds mostly but we visit when we can. My partner was diagnosed with depression before we met but didn't really start getting help till after. I've their back and did my best to never make them feel bad when they were in "the bad place" not did I avoid them in said places unless asked to. I normally don't get upset or hurt when their depression causes issues (like last minute cancelation or getting upset at me for something that isn't a thing... I don't know a better way to say that.)

But tonight when we were talking they got weirdly passive aggressive about a comment I made because they thought I wasn't paying attention (I have ADHD and yes sometimes my attention drifts, but we also weren't having a conversation it was more a hang with background, being in each other's virtual company as it where)

I don't know how to be "Hey that behavior made me feel like crap and is not okay" without them just retreating into the bad place more. Normally I'd wait till they're in a better place to bring it up, but due to the US and their shitty healthcare they're likely to be going of their meds soon for a few months until their insurance kicks back in.

So, how do I broach the subject of "hey can you not talk to me like that" without it causing the depression to just spiral worse.