Pond Boss Forums INTRO Questions & Observations Skinny Fish

Do nothing over winter.
Next spring, restart your feeding program, and prepare to decide to fertilize once water has risen, and temps are constantly in the 60's. Clear water, fertilize. Low visibility, let's talk.
Too early to worry about bass growth. Focus on the food chain, then make decisions about your bass next summer based on water clarity and pond size. Your pond is small enough to make drastic changes if need be. But, as long as you are seeing variation of sizes of bluegill, and your feeding program is working, make decisions about bass later.
If, by mid-summer, you weigh and measure 30-40 bass, and compare relative weights at that point, and 80% of your fish are seriously underweight, consider culling.
My experience has shown newly stocked lakes are resilient enough early on to correct themselves, unless bad decisions in the beginning doomed the fishery.
Your decisions were solid. Stay with them, for now.
Blue herons are probably not relevant for your situation. Even though they eat fish, their impact is minimal for the big picture.
Muddy water definitely has an impact on bass growth. Bass are primarily sight feeders. But, it's a double-edge sword. Muddy water protects bluegill and fathead minnows.
When your lake fills, forage fish will spread out, spawn well. As well, bass will spread out, food will increase, and bass should grow actively.