I'm working on a character rn and was using this light set: https://www.deviantart.com/second-circle/art/SC-Free-HDRi-Lights-for-Daz-Studio-646475146 basically to look in the iRay viewport to see what it looked like. I wanted to see what other light sets looked like with it so I tried to use this: https://www.daz3d.com/hdri-photoshoot I noticed none of the lights I was putting on looked anything like the preview. I had a feeling I somehow had both lights on. So I tried to go back to the other light set to check and lo and behold now it's different... This is from last night when I was using one of the free lights

and this is just now:

pls help

I don't have these lights, so I can only go by the description of them.

They sound like they are HDRI files and render settings, with no free standing or other lights.

Make a new file and apply your original lights. This should get you back to your baseline. Save this scene.

Go to File > Merge and select your model scene. Save this as a new file.

Try rendering it out and see if the lighting returned to what you want.

so they both look like HDRI's as Jason mentioned, I have the sc ones but not the Daz set. It shouldn't be possible to have both at the same time as they will overwrite the environment map render setting. what might have happened though is it looks like your dome rotation has been changed.

Find your render settings pane (if its not visible go to the menu at the top > Windows> panes > render settings) go to the environment section at the bottom.

for the SC hdri's (assuming you used the beauty dish one based on the colour) set environment mode to Dome only, Dome mode to infinite sphere, all dome orientation to 0, and dome rotation to 0.

This should give you the same result as the beauty dish preview.

Also check to see if the camera head light is on or off ( cameras tab ) If its on and the camera is close to the subject, and its set to rernder ( render settings check box) then it will make the light set look very washed out. I always turn my headlamp off and if needed use a fill light i can control instead. To sort your situation, load the scene, remove all lights from the scene tab ( if there are any) and also delete the envirments settings from the scene tab too, this should reset ds to the original hdri. From there you can load the lights you want. Another thing to check is under render settings / environment - if your using hdri settings you need to have dome and scene turned on, it might be that something in one of the sets has reset the environment to the day/time of day settings, again this will suddenly make all of your lighting load wrong.