relpages sudden increase

I currently do nightly database dumps on a ton of small dbs that are
increasing around 2-3mb per day. Suddenly, in a recent backup file, one
db in particular jumped from 55mb to 122mb overnight.

I did some investigation -

One table increased from 8mb to 31mb during a 24hr period. The table is
just text so this is highly unusual given that the number of rows DIDN'T
increase any more than normal.

pg_toast increased from 8mb to 27mb during the same period.

The relpages for the table in question increased from 164 to 1088 during
the 24hr period. On the live db, the relpages is back to 164 but the
size of the table remains massive.

Using Centos5/postgres 8.1.21 at the moment. Planning to upgrade over
summer but not had issues like this before on 8.1.

What gives?!

Thanks
Rich