From someone who has killed any number of plants over the years, I would say your citrus are looking passable.
And I really am no citrus expert but a couple of things...
I didn't really notice much leaf curl, it's more often an actual leaf miner and yours don't look like that. I think the leaves look a bit chlorotic (yellow) which could be a deficiency in... iron or any number of things.
The combination of seasol and powerfeed is good in general but just depending on a number of factors and particularly with citrus, may not be the best if used constantly.
I looked up the powerfeed data and it's Nitrogen 12/ Phosphorus 1.4 and Potassium 7. That might just be too little phosphorus to translate to good leaf growth and flowering. You might need to switch to a more citrus-geared fertilizer to use in the growth times autumn and spring.
We've talked here about citrus reaction to root competition, in that regard I'd be inclined to chop out the grass that's a bit too close, and mulch so that the roots get a bit more protection and that will also remind you to perhaps fertilize right out to the drip line of the plants.
The watering- you might do better with a loop and a couple of drippers than the spray and those can be set under mulch too to save evaporation.
I've also wondered how close your neighbour's plantings (over the fence) might be - looks like at least one banana, they will certainly be heavy feeders and enjoy going looking for nutrients, another reason to fertilize your plants a little more.
Before you commence anything though you might want to do a soil PH test just to see if you are fighting anything overly acidic or alkaline, as your plants would not like either.

I have a mandarin tree and all I basically do to mine is spray it with eco oil every year and put some home made compost around it,they do get sap sucking bugs on them if you don't spray and these do affect the tree badly,fruit starts to drop etc,you said you had your trees in part sun,madarin and orange and lemon all like full sun.dont keep pruning the trees every year just do it once to tidy up the low branches and then just leave it.also watering once a week is more than enough.