Hi, what I would do is scrape 2" of soil from the top of the pots, and top up with fresh compost, mixed with a handfull of growmore general fertilizer, Derek.

Hi again, I forgot to mention not to do it until spring, Derek.

I've got acers and I feed them with miracle gro dissolvable powder in the watering can, from about march to October everyday once a week, used it on everything in the garden last year and it was perfect :) great results! I can post a link to it if you like?

Fish Emulsion! It stinks to high heaven, but your plants will absolutely love it. Fish Emulsion fertilizer has macro and micro nutrients. Wait until Spring, then throughout the growing season.

Makes me recall that the coastal native Americans when planting corn manured the holes they dug out for seeding corn with some herring.

Makes sense... Mind you if those tubs are on a patio near to the house the fish emulsion is going to be particularly foetid
I take it the compost the Acers are in is acidic Taz.

Dilute it in water, not full strength.

Just wanted to say I love the view on your Avatar! Reminds me of where I was bought up.

thanks everyone for your answers, you have all given me a great deal of good advise, come spring I will try each way of feeding on different pot and look forward to seeing the results,(the fish one on the pots further away from the house) the acers are in compost with some john Innes no 2 never had a problem with them, just thought they may need some extra feed. I do take some of the top compost off every couple of years.

Acers will love Sequestrine, once they start into growth.