Cause of yellowing

[stinkyattic]

you would want your ph to about 6.0-6.5
I think the tips going brown could be a little burn, but with your ph being 5.5, it affects the absorption, while the plant is draining the food from those leaves, causing the yellowing as a sign of N deficiency. It might be best to stop feeding, adjust your ph, and give water, it will mix with the ferts already present in the soil.

This is absolutely on target. Excellent advice. Flush, test runoff pH. Adjust.