What is the meaning of "b'Yom Nit'ech Tesagsegi"?
Rashi: It is an expression of entangling. Your branches became confused with kinds of grasses and mixtures that ruin tree branches. I.e. where I planted you to be a vineyard for me, you messed up your deeds - "b'Yom Bachari v'Yisrael va'Esa Yadi l'Zera Beis Yakov va'Ivada Lahem b'Eretz Mitzrayim", "va'Yamru Vi v'Lo Avu Lishmo'a Elai" (Yechezkel 20:5, 8). Also here, you mixed with the abominations of the Egyptians.
Radak: Initially, when you followed ha'Kel ha'Gadol, you succeeded in your deeds. E.g. if one plants a sapling, and Yisga (it thrives) on the day of planting, and in the morning it sprouts flowers. So all your deeds were proper, and there was great Brachah in them.
Malbim: Not only did you graft a foreign, inferior species [onto the beautiful tree] - you strove to make it sprout immediately, the same day that you planted it, and blossom the next morning.
Why does it say "uva'Boker Zar'ech Tafrichi"?
Rashi: Afterwards, when I took you out of there, I entered you into Eretz [Yisrael], also there you sprouted evil seed.
Rashi (from Tanchuma Shelach 21): Before the heat came, you sprouted. A vineyard normally sprouts when the heat comes; it is not proper to sprout in the morning.
Refer to 17:11:1:2-3.
What is the meaning of "Ned Katzir b'Yom Nachalah"?
Rashi: A stack of bad harvest that was placed during the day became ill (reached a day of affliction). "Ned" is an expression of height - "Nitzevu Chemo Ned Nozelim" (Shemos 15:8), "Kones ka'Ned" (Tehilim 33:7). Ned is not the same as Nad.
Radak: Now that you corrupted your ways, the sapling and harvest shake.
Malbim: Even though you strove to make it sprout immediately, your deeds will not succeed. On the day, a great flooding river will wash away all the harvest. The Nimshal is, they requested help from other nations - but when they needed the help, the helper (Aram) was flooded and exiled.
Why does it say "[b'Yom Nachalah] u'Che'ev Enosh"?
Rashi: You received your 'wages'. "Enosh" is depressed with an evil illness, like "va'Ye'anesh" (Shmuel II, 12:15).
Radak: On the day that the great blow and mortal pain came to you.