When I started batches of mead and wine earlier this year, I racked off the lees that had formed when my batches were at the halfway point. Fermentation stalled in all the batches afterwards, and the impression I got from that experience and the responses online was that this was a bad decision that only outdated sources recommended, and that I shouldn't rack at all until terminal gravity was reached. Now I'm working with fruit meads using Lalvin 71B and what I'm reading online is that this should be racked a few days after fermentation starts to get it off the initial lees and avoid off flavors that 71B is known for.

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What are the hard rules for racking during fermentation, if any? Is it better in general to let fermentation finish completely before racking while 71B and certain yeasts are worth racking partway through? Or is it normal in general to rack partway through with all yeasts, and I just needed to add nutrients to help the fermentation restart?