I painted my daughters room a very similar shade of yellow. 24 hours later it looked like that.
It took 4 coats to finally get full coverage.
My guess is you just need another coat (possibly more) of yellow to get it to cover.
That’s mildew. Whatever cleaning you did before you painted did not kill the mildew spores. You painted over all of that and the mildew is growing again underneath the new paint film. Now you have one heckuva mess. I think the only thing you can try now is to saturate it with a mold killing chemical like concrobium and pressure wash the heck out of it and start over. But even that might not work.
There is a mold prevention additive that can purchase next time to help prevent mold, but as others have said when it comes to exterior paint can't cut quality paint. I like the colors they both go good together.
A forum community dedicated to Do it yourself-ers and home improvement enthusiasts. Come join the discussion about tools, projects, builds, styles, scales, reviews, accessories, classifieds, and more! Helping You to Do It Yourself!