Remedy for high alkaline soil?

Before I begin, here's a tip. Never trust a bag of soil, even if it says 5.5 pH.

I made a soil mix from palm dirt, biohumus, and perlite. The plant was doing good at first, but after a couple of weeks, I started to notice some nutrient deficiencies.

I checked the water runout in my soil mix, and it measures 7.1 pH. So that explains the calcium/magnesium deficiency and lime-green leaves.

My question is: Is there any way to simply correct this without making a correct soil mixture and transplanting it?

Thanks in advance.

Looks like I found my answer... it looks like adding sulphur will fix the pH. I just wanted to see if someone has some experience in this.