First of all, 네 in 하네 is not "you." 잘하네 means you did well, yes, but a more correct and direct translation would be: you're doing well. 잘했어요 means: you did well. (Or literally, good job) The ending "했어요," or "했-," means something is done in the past tense. On the other hand, "-하-" implies the present in most cases. The ending "-네" does not necessarily change the meaning of the entire sentence. According to the Korean dictionary, "-네" is "an ending used to describe what we have (just) realized. Often implies admiration, awe, or is exclamatory." In this case, 잘하네 basically means you are doing well, but it may differ by context. For example, a teacher might say "잘하네" to a student who is doing well. In another example, if the teacher's expectations on the student were low previously but he/she turns out to be excellent, the teacher might also say "잘하네," but in a slightly different sense. In this case slight amazement is implied. Again, the general meaning does not change; the endings(such as "-요" and "-네") only slightly change the meanings that the sentence implies, or depends on the relationship between speakers. Another thing is that "잘하네" is usually directed at people younger or lower than the speaker. This is because it does not include the ending "-요," as in "잘했어요." It includes the ending "-요," which is honorific(polite language). Sentences that end with "-요" isn't necessarily directed at people older or higher than the speaker, but it is used with respect and politeness. For example, teachers may address the students using "-요." So basically, "잘했어요" is polite, whereas "잘하네" is relatively informal. If you have any more questions, feel free to ask me. Hope this helps!

Your guess is wrong. 네 is an ending particle used for exclamation of knowing a certain new information. 네 can be followed by 요. There is also 군(요). 잘하네 literally means "I didn't know that you are doing it well." For more detail, Refer to https://www.italki.com/question/370652