The next time you grow, I would stay away from the "moisture control" stuff. Staying wetter is typically the wrong direction to go. Also pay attention to the NPK values printed on the bag. That moisture control potting mix is 0.21-0.11-0.16. At that level, it could burn. Or, at least you wouldn't want to feed for some time (and often people don't know when to feed. In that sense it's better to use a potting mix with low values, and add light nutrients each watering. If you wanted to do that, MG Organic Choice is better. NPK 0.10-0.05-0.05.). Another problem with pre-fertilized soils (especially MG's pre-fertilized soils) is that the fertilize is usually time-released. The more you water, the worse it gets (as nutrients are released). You might have dodged that bullet by mixing it with the MG peat moss. But, MG adds fertizer to that too(!). 0.19-0.11-0.15. They add nutrients to everything. Organic Choice is the only thing I've seen people use, and like the results. But, you should add perlite (at least 25%) to that. (But, again, if you use MG's perlite you should soak/rinse it first because they add 0.11-0.11-0.11 to their perlite too.).
I think your problem is that you're not saturating the soil for 10% runoff, and then letting it dry substantially. It sounds like you're giving it sips every couple days. Some areas would be dry, other areas kept to wet.
Also, I wouldn't have a plant way below the edge of a container. I see people do that, and it seems like it would inhibit air flow, reduce the light. I would put the plant in a proper-size container, fill it to the top (almost) with soil. If you have something taller than you want to fill with soil, use a hacksaw and cut it down to the height you want.