NJ.com look into this (https://archive.is/3ysCV). For (1) 6 is not an unprecedented number of whale deaths as there have been a few whale deaths every year in that region for the last 20 years. NOAA is investing sudden increase in whale deaths since 2016, but states that "so far no humpback whale deaths have been attributed to offshore wind activities".

For (2), from my understanding building offshore wind farm causes some local disturbance to aquatic life due to the construction works. But it's fairly limited in time and space. Compared to for example ocean deoxygenation resulting from i.a. climate change, construction of offshore wind farms that try to help deal with climate change is a minor threat to aquatic life.

You don’t really need to debunk the second one. Even if you accept the premise you could just argue that the amount of ecological damage, even if severe, is nowhere close to the damage done by offshore drilling, oil spills, and the burning of fossil fuels. It doesn’t have to be perfect to be better.

Just two general thoughts, not a debunk in itself:

2. offshore wind farms pose a severe threat to aquatic life.

Any work, or simply presence, in any ecosystem will harm some life there in some way. That makes the statement "X will harm marine life" a bit pointless. Quantify the statement to make it worthwhile: How much harm does it cause, and how does this harm compare to other, similar activities? Especially interesting questions might be: Does it cause unecessary, or avoidable harm? If we don't do X, but Y, how much harm would Y cause instead?

1. 6 whales have been killed by wind farm development in the last month

Again I'm missing context. What's the opportunity cost of not building offshore wind farms? For example, how many whales are killed by oil spills and other energy related activities which could reduce if we build more wind farms? Not saying wind farms are better (although I believe they are, but that's not the point), just saying we need to put the numbers in context to make sense of them.

In summary, it's easy to find bad things about anything. To decide wether an option is still a good or even the best option, we have to compare it to the other options (all of which will also cause harm).

2. offshore wind farms pose a severe threat to aquatic life

The issue is the "severe" portion. Running wind farms do cause noise, but it's 10 to 100 times less than from ships. So it's unlikely to be much of a change.

The construction (pile driving) is more problematic, but you can mitigate that with bubble walls. .

It is plausible. Some (possibly most) whales use sound (low quality sonar) to figure out where the shore is. Most food is within a few miles of shore (unless ocean currents push or heat the food at the bottom in a certain way in some oceans where there is tones of food in the ocean for miles.

Regarding this specific claim, if there were to be large masses that react to sonar (wind farms) that are in a grid, it could seem like a "shoreline" to a whale, and it could confuse the whale enough to beach while trying to find food, a mate, or a place in the ocean to rest and breathe. However, with the given information there is no conclusion other than "there might be a correlation" without more data.

In contrast, certain costal military bases have submarines that accelerate so fast that the propellers cause cavitation (sudden phase change of water from liquid to gas from low pressure). These submarine's cavitations & related cavitation collapses creates a kind of "turbulence" underwater but it sounds MUCH MUCH worse. Whales have been distressed in those areas for a while and after a generation or so, only the adolescents or "foreigner" whales get confused enough to beach anymore. Again, there is not enough information to have a conclusion other than "I think this is a correlation, we weren't tracking that before, but it seems to explain what we are observing".