Grainy Photos when cross-developing in Photoshop

Hello there. First off, I shoot using a Nikon D3400 and only shoot in RAW format. When I'm developing my photos, I start in lightroom, and only when absolutely necessary do I jump the photo over to photoshop to do extreme editing. The problem is, whenever I do so, the photo ends up being so grainy that not even noise reduction edits can fix it and it looks like I took the photo with an old flip phone. Does anyone have any idea what might be causing this? I'm hoping it's something simple, hopefully a setting I messed with a not a glitch in the program, as I can't wait for them to fix it. I have an important gig this weekend, and it's going to involve a lot of moving the photos to photoshop, as it's a green screen photoshoot. I know that I could export the photo as a JPG then pull it into photoshop. But I would much rather do things with the plugin. It's faster and less memory. Plus there are less steps, and time is going to be crucial.