Three lights appeared moving in the sky then dissappeared

Local weather: KDCA 070252Z 16005KT 10SM FEW060 FEW085 BKN150 22/19 A2989 RMK AO2 SLP120 T02220194 58005 (I live about 3 miles from DCA)
[DECODED Weather:
Temperature: 22.2°C ( 72°F)
Dewpoint: 19.4°C ( 67°F) [RH = 84%]
Pressure (altimeter): 29.89 inches Hg (1012.3 mb) [Sea level pressure: 1012.0 mb]
Winds: from the SSE (160 degrees) at 6 MPH (5 knots; 2.6 m/s)
Visibility: 10 or more sm (16+ km)
Ceiling: 15000 feet AGL
Clouds: few clouds at 6000 feet AGL, few clouds at 8500 feet AGL, broken clouds at 15000 feet AGL]
About me:
I rent this apartment (since 2017) because of the panoramic view facing east and because of the proximity to Washington/National (DCA) airport. I am passionate about military and civilian aviation and, as a result, I spend an inordinate amount of time looking at airplanes [noting their make/model, company (owner), path, assumed route, and deviations], weather, and the sky.
My Observations:
On Wednesday, 04 October 2023, at approximately 1910 local, while sitting on my easterly facing balcony with a friend, talking, I was facing approximately NNE. I observed three lights that "popped into my view", suddenly, causing me to say "whoa" out loud. I did not have to point out the lights to my friend, I simply said something like what are those lights in the sky over the Kenedy Center. She observed the same lights and had no idea what they were. I observed that three dots heading together in a due north direction, at a satallite's passing overhead speed, in an open triangle formation. The three lights were on a triangle, with one light "leading" the formation to the north and two more lights all equidistant from each other to the south. These did not look like the Starlink sattelite pattern of lights so frequestly seen in the sky. Then, within a minute, they all disappeared, first the most northly, then the other two, one after another.
The lights were a whitish (with a hint of blue) color. There was no variation in color. There was no variation in the path nor movement. The lights appeared about 35 - 45 degrees above the horizon. They appeared that they were over the surface a great distance away, guessing maybe at least 75 miles away(?) if they were even within low earth atmosphere. They were possibly operating (as I suspect they were) in space. There was no sound.
I knew the sun set recently, so I first considered what I was seeing to be a reflection. I disregarded that because the lights "popped" into view versus gradually illuminating - plus, I should have seen a "reflection" well before passing so far north in the sky. (In other words, since the lights traveled south to north, perpendicular to the sun's path, I would have seen any reflection that high in the sky much, much sooner in the more southern sky.)
My next thought was that I was seeing satellites - but satellites do not fly in triangle formation in "close" proximity to each other. We did see a satellite later that evening that I suspect was the space station traveling overhead from west to east and very brightly illuminated. The three lights looked completely different.
I am familliar (very) with UFP/UAP history, incidents, and converasations, etc. My initial reaction was not that I was seeing a UFO/UAP, but was a "head tilting" but was a "what the heck was that" reaction. Then I concluded that, from my perspective, since it was unknown to me, it was, by definition, an unknown flying object / unknown aerial phenomena.
I thought of trying to take a picture, but I know from experience that my cell phone would not have captured the lights.