Please help me. This has happened over night.

Your friend's plants are suffering from a Calcium deficiency. A calcium deficiency can appear like a ton of brown spots overnight on leaves. Typically a calcium deficiency is the result of one of 3 things: Low ph at the roots, too-pure water for example RO/Reverse Osmosis water, filtered water and not using nutrients. Another possible causes could be LED grow lights, plant leaves work hard under LEDs, which is how they get great yields, but it also makes plants more prone to deficiencies.