About the mushy one: it sounds that you've tipped it from its pot.

Is there anything left? Preferably with at least one root and a bud point.

If yes - think about planting it into cactus mix and keeping it averagely moist over the summer - with shade protection for the hottest part of the day. Expect it to take up to three years before it bulks up enough to flower again. Be sure to use a close-fitting pot. It is fatal to over-pot.

About over-wintering: I notice when I bring things in for winter it takes MONTHS for the potting mix to actually dry out. Like from May to August-September. Your Agapanthi may be sitting in cold damp conditions for too long. Can you snuggle them a little closer to a source of warmth? Somewhere that stays mostly around 50F (air temperature).

And seriously ease back on the watering over late autumn. Give it time to go into 'drought' mode.

When you get to the end of winter - LIGHTLY water to start to 'break the drought.' It takes time for the roots to get back to work - or even to grow new ones for the coming season. (Look at a bearded Iris rhizone at the end of summer to see what I'm on about.) When you see top growth - water again, but leave the drenching until it's really obvious that there are enough active leaves to cope with the amount of water you're adding.

My dwarf Agapanthus lives in an 14" high and wide container fully outdoors. The clump has nearly filled the top of the container. It now flowers reliably after being a rescued scraplet of plant. I usually topdress with some fresh mix in early spring (August) and sneak it some slow release pellets. I don't remember watering it over summer... and it's been around for about five years now. Just rain. (If you don't get some summer rain you probably need to give it a drink from time to time.)

The big evergreen Agapanthus grown by the neighbour lives in appallingly cramped and sunblasted conditions in tiny (9"x24") 'beds'. Never watered. Never fed. Just gets falling leaves. Flowers for months, and spits its papery seeds into every crack along the gutters - where they come up like grass. A true Monster!

Hope there are some clues there. If they weren't such thugs - they'd be great!

Thank you so much for your help. I think that bringing the pots in for winter is where I went wrong. I bet they weren't dry enough. I have 6 pots with various sizes and nothing ever flowers except when I bought them in full flower! I have taken the pieces of growth with good roots left and potted them up in small containers. Will put them out in the garden. Until they all get pot bound again, I don't expect flowers. Maybe there will be a surprise? What would you use for a fertilizer?