Now I can see three things wrong there:

Too much sun first and foremost.

Next the sun is heating the medium which causes a ph change.

Strong sunlight means strong growth, unless the plant can't handle it. It starts to draw nutrients from other parts.

Of course it could be a strong plant and lives thru this to cooler weather and sun. It'll build up strength and come back much stronger next year. Just remember you win some you lose a lot. But so far nature gives us plenty to practice with.