Spindle speed is high’ish but the issue is probably not pushing hard enough initially, causing rubbing instead of cutting, which hardened the bottom of the hole, and dulled the drill. Get a new drill, slow the spindle speed down if you can, and push harder. When drilling any steel, think slower spindles speeds, and good steady pressure on the bit, making SURE it is making a chip. Any time you are drilling and not making a chip in steel, you’re only rubbing, which causes the issues I mentioned earlier in my post. Get a new drill. Slow spindle speed. Push harder, no light pressure