Jagmanjoe, the one thing you said that caught my attention was that your fertilize your mango regularly. Depending on what you fertilize with that could be your problem. If you are giving your tree a lot of Nitrogen, it will grow lush and green but may not do much for you in the fruit department. While it needs some N, it should not get too much. It sound counterintuitive, you think a healthy green tree should make lots of fruit but it is not necessarily so. You don't want your tree trying to make leaves when it should be making fruits
Other factors to consider is how much water - too little or too much is bad.
Google the topic "mango fruit drop" and you should see many articles.
https://homeguides.sfgate.com/methods-control-fruit-dropping-mango-31174.html
I appreciate your input Akin. A little quick history about where I am, just under 2 years ago when we purchased my first thought was I could really do some mango trees now. I quickly planted 9 mango trees of different varieties without a lot of thought. Then about a year ago the rains hit and all of my mango trees would constantly end up in standing water for days on end as I never realized just how wet our property is.
To counter that prolonged wetness, within each of the barrier areas I have dug out and placed 6" diameter drain pipe going straight down about 2 feet in 3 spots. I have fashioned a setup where I have a boat bilge pump on a pipe with a battery and handle so when it floods I can quickly draw about 6 to 8 gallons of water from each tree area and move it to the street. My fashioned system only takes about a minute per tube so I can do it several times a day if necessary when heavy rains strike.
While I initially fertilized the trees with time release fertilizer, in research I determined that this might not be the best course as wet as this property can stay, the time release can end up not lasting the intended several month timeframe. Accordingly I switched last fall to Diamond R SuperFruiter 6-3-16 with micros for now as my trees are still fairly small. It has very little time release so I fertilize monthly during the growing season at about 3/4 cup per inch of trunk diameter. Once they get more established, I plan to drop to a lower or no nitrogen fertilizer. Also when I fertilize, if it has not been raining for a week or so and nothing of significance is predicted, I water it in. I also water only when we have prolonged dry spells.
Early this year I had some great panicles on my Carrie and Cogshall but lost them during a freeze even though I had the trees covered with frost cloth. Trees suffered no damage other than panicle loss. I then had a super flush of panicles on my Ice Cream and smaller flushes of panicles on several others. They did produce some fruitlets but over time all dropped. I am guessing the trees just have not been in the ground long enough, particularly considering the less than ideal environment of the flooding issues. I am hoping that between them being in the ground longer and hopefully my controlling the flooding issues better this year, they will get better established and set some good fruit next season.
I did have a half a dozen mango trees that I planted at our previous home and the third year in the ground when we were just moving out were all loaded with panicles. -- just my luck. I should have negotiated the sale of that place to go back and collect some fruit for the first year.
I have added a couple of pics, one of the fertilizer I am currently using and the second of the first line of my original 9 trees here.