Textured Resin

Hello! I am trying to make a clear resin coaster, with pills floating in the middle. This is my first time using resin, and my resin isn’t totally transparent or smooth through the body of the coaster – There seems to be some ‘texture’ in the middle of the coaster. The coaster is smooth to the touch on the top and bottom, but when I hold it up to light the middle doesn’t look right. Ideally, I am trying to achieve a totally smooth and clear solid resin coaster. Additionally, when looking at the coaster from the side, you can see two separate layers of resin. The top layer appears to have more of the ‘texture’ than the bottom, but it’s a little tricky to tell. 

I poured equal parts of resin into a plastic measuring cup, stirred for three minutes then poured into my silicone mold. I poured three layers of resin (waiting about 8 hours in between each) and used a heat gun to remove bubbles each time. Then I let the entire coaster sit for 24 hours before removing. I made the coasters in a room that was about 70 degrees.  Do you have any insight as to why this happened? Any suggestions for what I can do to prevent this moving forward? I have photos that I can provide if that would help!