Our Cichlids - their short tragic history

We entered the hobby a few weeks back, and have a small 5 gal
aquarium running, apparently well, and decided to up the ante.

Well, we setup a planted aquarium round about christmas, and
added a few tetras, the ammonia spike happened, then subsided.
We read about bio-spira. So we rushed out, and got some, added
it in, and simultaneously added 3 Bolivian Butterfly Ram
cichlids (papilliochromis altispinosa).

THey turned out to be wonderful fish, and one soon established
himself to be top-boss. Recently, they started rearranging the
plants and rocks.

This morning, the nitrite spiked - the ammonia was still high,
though about 1 ppm. We did two water changes today, and added
some salt in the evening.

Unfortunately, the cichlids, and other fishes, were seen to be
gasping at the edges, and one went belly-up We thought a lot
about what to do, and finally transferred them to a bucket of
water. As I write, two are dead, and disposed, and one is
swimming round the bucket.

I would like some advice as to how this could have been
avoided, and what should we do next. Are the other fishes
(tetras and corys) going to survive? Will the water cycle play
itself out now and when will it be safe to reintroduce fishes?
Whatever happened to the biospira?

In gloom,
aacool
P.S. A pic of the cichlids is attached