I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
I don't think pH is the problem. Yellowing foliage is often due to periods of soggy wet or dry soil conditions. Try feeding the plants again with a soluble plant food like Miracle Gro and they should respond with new green growth. Try to maintain moderate soil moisture and make sure the plants are getting a lot of sun. They need full sun or close to it to bloom well.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
Q&A Library Searching Tips