Stuck Screws

[BradS7535]

So I'm in the process of converting the tube lights to LEDs by removing the ballast and installing the strip LEDs on the reflector. I was able to remove the fixtures over the stove, in the bathroom and over the rear bed, however 2 screws in the fixture over the sink are REALLY stuck good
I started to strip one of the heads trying to get it out. I noticed the 2 screws that are stuck are located towards the middle of the fixture instead of on the ends like all the other fixtures. Anyone know why these 2 screws might be stuck and the best way to remove them?