I planted a Thompson Seedless grape vine about a month back. The vine has been growing at a rapid pace after establishing itself; however the lower half seems to be losing vigor. The leaves are starting to spot black with a whitish haze on them. I also see some yellowish/brown spots on the leaves (please see pictures). The growth buds appear to have lost vigor and easily fall off.

Based on my research on the web, it appears to be downy or powdery mildew, or both. But I am not sure. I need help identifying the cause and possible remedy.

I keep the vine fairly dry on the leaves and there are no other grape vines nearby. I really would like to save the vine. I am considering neem oil application on the leaves. Not sure if it'll be enough though.

Thanks!