The plant seems to be sane, the fruit could have Coryneum?

I have the same thing this yr. I think it's a reaction to the thrips damage. Peach/nectarines often throw out that type of sap in reaction to damage on the branches. I don't think it's anything to be concerned about past the usual thrips damage.

Lacking in vigor because there is no new growth and few leaves in your picture. Peaches/nectarine should look more like this: Something like malathion will usually kill the scale. In winter treat with dormant oil to smother the over wintering forms. You can't wash them all off. And usually there are the big adults and smaller ones that need killing as well. Many people use a copper product like Kocide 3000 https://www.keystonepestsolutions.com/kocide-3000-fungicide-4-pounds-387 for PLC. It must be sprayed before bud swell in spring. Spraying later does nothing. If bad spray fall, winter, and early spring.

Agree too much water...make jam!