If you watered on the 28th and you haven't watered since then they are probably under watered. Someone mentioned MG. the burn could be from your soils nutrients. If you MUST use MG then you should mix it with plenty of pearlite to help with drainage. Thats probably why your soil is still wet after almost a week without water.

The moisture meter that LUDA suggested will really help. If you're testing your pot and its telling you your soil is still most 5-7 days after you've watered then you have a moisture lock problem and need to do something about your drainage.

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