Just a heads up, Growgreenseeds.com has a DVG drop today. US seed bank out of Washington. I want to see this company succeed because they are so close to me and do good business.
Your ph is a little low, but not that low. I don't think it is the cause of your problems but Ideal PH for soil is 6.5. Raising it a tad wouldn't hurt you.
Important thing to do is to take your time and be sure what the problem is. Trying to fix a problem that doesnt exist can worsen the real problem. Wait for more opinions.