First picture looks like watery urates (urates are the white part of the dropping) and second looks like shed intestinal lining.
How are they behaving? In 7 week olds with droppings like this if you see any signs of lethargy, not eating or drinking well, sitting puffed up, I would treat for coccidiosis. Additional symptoms are runny or mucousy droppings, and sometimes bloody droppings. It's very common in chicks. If in doubt, I would treat, the treatment is very safe. Treatment is Corid, available at Tractor Supply stores and many feed stores, it will be in the cattle/livestock section. Either liquid or powder can be used (pictures below). Dosing chart below,
use the severe outbreak dosing always. Treated water should be the only water available and no vitamin supplements during treatment as it could reduce the effectiveness of the medication.
Occasional intestinal lining can be nothing to worry about, but since coccidiosis can kill pretty quickly, if in doubt I would treat.
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