Two years running we had to get a pool started from scratch, owing to a liner problem. In adding water this year, we went from normal looking water (with tons of leaves on the bottom) to a green-tinted pool just after adding well water.

Well, last year we had a similar sort of issue and while I was tending to blame it on metal in the water, I kept hitting it with bleach for a few days, and I changed the DE twice in the same time frame and the whole thing cleared right up. Were I you, I'd just keep that pool at shock level for a good long time, and keep on changing out the DE every few days or so. Once you get the pool clean, you won't have to change the DE very often at all, but during the start up phase, it can get junky pretty easily. When mine gets junky, it definitely affects the return flow negatively.

Good luck!