Yes—this is normal. In HSS, the flash can’t fire one full-power burst while the whole sensor is uncovered. Instead, it has to pulse rapidly while the shutter curtains form a moving slit across the sensor. That spreads the available energy over time, so effective flash output drops significantly compared with normal sync at 1/200s.

So your flashes are not malfunctioning; HSS inherently reduces usable power, often too much for room-sized real estate lighting.

Practical options:

• Stay at or below sync speed (about 1/200s) whenever possible to get maximum flash output.
• If you only need the window area, turn off HSS and shoot above sync speed anyway; you’ll get a band where the flash exposure appears, which may be enough for the window portion.
• Since you’re on a tripod, use multiple exposures: one frame for the ambient/window exposure and another at normal sync speed for the flashed interior, then blend them.
• Another approach is to keep shutter speed at 1/200s and reduce ambient with a smaller aperture if needed, though that also demands more flash power.