Hi and thank you for your question. Your plants don't look yellowed in a chlorosis-related way, which is great. The slight discoloration looks more like sunscald. Were your plants inside or in a greenhouse prior to planting? If not hardened off properly by gradually introducing full sun to them before being planted outside, they can easily be burned from the sun. They will, however, outgrow those scalded leaves and be just fine.

That being said, if the bleaching continues, it may be related to the chicken manure. Was it well composted before use? Manure that is not aged is very high in nitrogen, which can burn young plant roots.

To summarize-- wait and see. The discoloration on your plants looks abiotic and they will, most likely, outgrow the issue. If they don't, it is due to the manure and the best thing would be to plant elsewhere until the nitrogen levels reduce. The pH does not look like it is the culprit. 

Note: coffee grounds, while adding carbon to the soil and a fine additive to a compost pile, do not tend to effect pH levels. The soil acidifier alone will do the job.

That does sound like the culprit. They look okay, considering, and I think they will rebound just fine. Happy gardening!