Three things must be present for mold to grow. First, mold spores, which are everywhere and you can't eliminate them without sophisticated equipment. Second, food, either in the form of organic cork material or wine seepage, it seems food has been provided. Third, moisture, either from wetting the corks, wine seepage, or high humidity. Higher temps make the growth conditions even more favorable.
The temps that you describe in your original post, 23 - 28 C (73.4 - 82.4) are too high, though the lower end of the scale is probably ok for short term, you should never let your wine get into the 80's. The fact that you have varying temps means that you are having pressure changes inside your bottle as well, and when stored on their sides, with a poor quality cork, wine may be squeezing out of the bottle around the cork, which is where your growth seems to be. Additionally, you didn't mention anything about the humidity level in your storage area, high humidity promotes such growth, and the capsules, though they are designed to let air in / out, are helping to hold the moisture there for the mold to work with.
As far as your crumbly corks, that usually happens with corks that are in an arid environment, or are old, and have dried out. You don't seem to have an arid environment, as evidenced by mold growth. All I can surmise is that you started with bad corks in this instance.
Seems to me that you have two issues, bad corks and poor storage environment, and would suggest a few things for you to consider, some of which have already been mentioned.
1. Buy good corks, 1-3/4", #9 corks, good quality cork, 1 + 1, or go to completely synthetic corks. The last statement in the description of the corks you are using says: "Please note cork design may change without warning". You really don't know what you are getting, but suspect you started with old, dried out corks.
2. Stop soaking your corks in sulfite solution, put them in a strainer in a closed container with sulfite in the bottom so the fumes, not the water, sterilize them.
3. Figure out a better place to store your wine so that you can control the temps and not let it get so hot, nor let it fluctuate so wildly.
4. Leave your wine standing in its final storage area for a couple of days before capsuling.
I don't believe that the capsules are causing the problem, but highlighting some other deficiencies.
The temps that you describe in your original post, 23 - 28 C (73.4 - 82.4) are too high, though the lower end of the scale is probably ok for short term, you should never let your wine get into the 80's. The fact that you have varying temps means that you are having pressure changes inside your bottle as well, and when stored on their sides, with a poor quality cork, wine may be squeezing out of the bottle around the cork, which is where your growth seems to be. Additionally, you didn't mention anything about the humidity level in your storage area, high humidity promotes such growth, and the capsules, though they are designed to let air in / out, are helping to hold the moisture there for the mold to work with.
As far as your crumbly corks, that usually happens with corks that are in an arid environment, or are old, and have dried out. You don't seem to have an arid environment, as evidenced by mold growth. All I can surmise is that you started with bad corks in this instance.
Seems to me that you have two issues, bad corks and poor storage environment, and would suggest a few things for you to consider, some of which have already been mentioned.
1. Buy good corks, 1-3/4", #9 corks, good quality cork, 1 + 1, or go to completely synthetic corks. The last statement in the description of the corks you are using says: "Please note cork design may change without warning". You really don't know what you are getting, but suspect you started with old, dried out corks.
2. Stop soaking your corks in sulfite solution, put them in a strainer in a closed container with sulfite in the bottom so the fumes, not the water, sterilize them.
3. Figure out a better place to store your wine so that you can control the temps and not let it get so hot, nor let it fluctuate so wildly.
4. Leave your wine standing in its final storage area for a couple of days before capsuling.
I don't believe that the capsules are causing the problem, but highlighting some other deficiencies.
