I'd wait until later so the bulbs get the benefit of fresh mix and food for growing on over winter-spring.

Another plus would be - usuing your planters over summer for a different display and then refreshing with the bulbs and hardy cover plants for winter-spring.

OK, should I water or fertilize at this time?

If you had to break roots - and trim back the leaves - there's not much growing system left to cope with plentiful water or food. Rot is likely at one end or t'other if you're generous.

Unless you know you're going to get little or no rain for a few months to come - stick with the rainfall you get, so long as your container is well-drained (generous holes, clear of the ground).

While there are still leaves you could give something like a very dilute liquid fertiliser that is evenly balanced. The potash in the mix helps the bulb to harden off and form buds for the following year.

Let the holding tub's mix gradually dry off over the summer so the bulbs go into dormancy. Once they're hardened off and have good insulation from the soil, they don't mind being dry.

If your mix has Those Water Crystals (humph!) added, be particularly careful with watering - far more frugal than you'd be with a plain mix.