Tomato fertilizer should have high phosphorus than nitrogen and there is no need for the wood ashes so they should not affect bloom. Acid soil is fine.

Do you hard prune it every year? Jackmanii blooms on new growth.

Has the amount of sun it gets changed?

I prune it down to about 6 inches in early spring. I'll stop the wood ashes...don't know what else the problem would be. It's in full sun, roots shaded.

Try a bloom booster type fertilizer.