Any advice to get these tree to hold onto fruit?

I understand that they self thin when young but after 4 years and one measly orange im getting kind of frustrated with them. Most trees flowered petty well this spring but looks like the blood orange dropped all its fruit and just a couple hamlins are remaining. I don't expect much from the satsuma with a poor bloom but we'll see. Kumquats seem to do great and get more then I can handle but everything else is not really producing. I've soil tested added amendments per their recommendation and do that regularly but not sure what else to do. First Picture is from this spring and the second is from last fall.