how do I care for lupins as blooms start to fade?

Cut off the flower spikes as the bloom fade and you will, hopefully, get a second flush of flowers.

Just done that today and as mg says you will probably get a smaller flower spike sept time. if you want to collect the seed, leave a few pods on to ripen and turn brown.

Yes the seed will be the size of a pea and can be planted where you want them to grow straight away or in pots.

Thanks to Moon Growe for advice on 'lupins after blooming'.

You are welcome Mae